Abstract:      As the largest developing country, China plays a role of the world factory, and its economic growth mode is mainly based on extensive manufacturing expansion. With the increasing scarcity of resources and environmental pollution, the problem of sustainable development in China is becoming more and more serious. Different from the traditional economy, the digital economy with information and communication technology as the carrier has become a new important driving force in the process of restructuring the world economic map promoted by the information revolution. China continues to emphasize the opening up of digital economy, while accelerating the green transformation of development mode and improving environmental quality. Therefore, in the era of green economy, the research of promoting the opening of digital economy is an important way to reduce environmental pollution in China.On this basis, based on the ICT trade data and industrial sulfur dioxide emission data of 139 Chinese cities from 2003 to 2016, this paper used the two-way fixed effect, threshold effect and regulatory effect models to investigate the impact of opening in digital economy on environmental pollution and its mechanism. The possible contributions of this paper are as follows: first, it measured the opening level of digital economy in Chinese cities, which can enrich the relevant research of opening in digital economy. Second, the study of the impact of the opening of digital economy on environmental quality from the prefecture-level city level can enrich the environmental governance literature at the middle level of the city. Third, the paper examined the impact mechanism of opening in digital economy on environmental quality from the perspective of technological innovation and industrial structure to provide empirical evidence for Chinese environmental policy making.The main conclusions include the following aspects. First, the opening of digital economy has a significant inverted U-shaped effect on environmental pollution. Second, the opening of digital economy and environmental pollution in the eastern region, the economically developed regions and the cities with high Internet development level show an inverted U-shaped relationship. Third, with the increasing level of technological innovation, the opening up of digital economy has more and more restraining effect on environmental pollution. Fourth, the coordination between the opening of digital economy and industrial structure can effectively reduce environmental pollution within a reasonable range, but when the industrial structure exceeds the reasonable value, the shape of the opening of digital economy and environmental pollution reverses, showing a positive U-shaped relationship, which means that the opening of digital economy will significantly deteriorate the environment.Based on the above research conclusions, we can draw the following enlightenments. First, China needs to connect with the international community, narrow the “digital divide”, sign digital economic development agreements with other countries, establish digital economic blocs, and give full play to the effect of digital scale. Second, we can strengthen the main ability of technological innovation. At the same time, the government needs to create a good model of digital green development and improve the efficiency of resource allocation by cultivating high-end production factors. Third, local governments need to adopt a reasonable industrial structure and adapt to local conditions to realize the coordinated development of industrial structure transformation and digital economy, which fundamentally reduce the unreasonable investment of resources, reduce energy consumption, and produce more income at a lower environmental cost.The research of this paper is of great significance to realize the harmonious and sustainable development of Chinese digital economy and environment. At the same time, it also provides a scientific study and lays a foundation for optimizing Chinese environmental protection policies.

Key words: opening in digital economy, environmental effect, technology innovation, industrial structure