As a new feature of financial development, digital finance can help to break the financial exclusion that traditional financial institutions conduct to small and micro enterprises, alleviate the misallocation of financial resources, reduce the enterprise cost of borrowing, and diversify R&D risks. Thus, it will stimulate technological innovation of enterprises and inevitably affect industrial development. Especially in the context of the new technological revolution and industrial transformation marked by digital technology, it is of great practical significance to explore whether digital finance stimulates technological innovation and promotes the upgrading of industrial structure for the establishment of modern industrial system and the realization of high-quality development.
    This paper firstly analyzed the mechanism of digital finance, technological innovation and its intermediary effect on the upgrading of industrial structure from the aspects of capital formation, risk dispersion and consumption guidance, and research hypotheses were proposed. Then, based on the mediating effect method, fixed-effect model was constructed, and the impact of digital finance and technological innovation on the upgrading of industrial structure and its regional heterogeneity were empirically tested on the basis of measuring the upgrading of industrial structure, technological innovation and other indices, combined with Chinese urban panel data. The empirical results showed that digital finance and technological innovation both promote the upgrading of industrial structure. The results of the sub-dimensional heterogeneity test showed that the breadth of coverage, depth of use, and degree of digitialization of digital finance all promoted the upgrading of the industrial structure. The results of the regional heterogeneity test showed that the promotion effect of digital finance in the central and western regions is greater than that in the eastern region, indicating that digital finance can help narrow regional gaps and promote coordinated regional development. The results of the mediating effect test confirmed that digital finance promotes the upgrading of industrial structure by stimulating technological innovation in China and the central and western regions. Based on the above conclusions, in order to accelerate technological innovation, promote the upgrading of industrial structure and coordinate regional development, this paper put forward some policy recommendations from the following aspects:
    (1) The development of digital finance should be promoted. Firstly, the government should lead the formation of a frontier digital technology research group to break down the technical barriers between regions, enterprises and scientific research institutes to accelerate the development process of digital technology. Secondly, a regional digital financial development policy should be implemented. The eastern region should make full use of good technical conditions, strong capital base and economic policy advantages to achieve major digital technology breakthroughs as soon as possible while the central and western regions should start with the construction of new infrastructure such as 5G, and make full use of late-mover advantages to achieve the leap-forward development. Thirdly, digital financial education should be strengthened. The small-, medium- and micro-enterprises or other groups in the central and western regions need to be guided to use digital financial resources correctly and expand the coverage of digital financial services.
       (2) The digital transformation of traditional finance should also be enhanced. Firstly, the integrated development of traditional finance with digital technology should be promoted; the limitations of banks and other traditional finance be overcome in terms of business network and operation time; and more inclusive development of traditional finance be promoted. Secondly, focus should be given on the theme of "scientific and technological innovation", and on such traditional financial institutions as the four major state-owned commercial banks of "ICBC, ABC, BOC, CCB" so as to promote the digital technology innovation process. Thirdly, the reform of the financial system should be further deepened to make the market play a decisive role in resource allocation, and financial support and preferential policies for small, medium and micro high-tech enterprises should be appropriately strengthened by financial institutions.
       (3) The technological innovation process should be accelerated. Firstly, regional innovation incentive policies should be implemented to meet the demands of different regional industrial development and market consumption. Secondly, various types of policies such as financial policy, industrial policy, fiscal subsidy policy and environmental regulation measures should be comprehensively adopted to guide the allocation of economic and social resources to enterprises in high-tech industries. Thirdly, a cooperation model between the government and private capital for technological innovation should be established to alleviate the problem of lack of funds faced by China′s technological innovation.