Many scholars have affirmed that universities paid an important role in regional innovation and they were at core position in national innovation system, but few studies have been done on the impact of “university enrollment expansion”on universities′ innovation efficiency. In theory, as an organization, the university has the characteristics of multi-product joint production including talents and scientific research innovation under the constraints of constant production technology and limited resource input, the expansion of university enrollment will inevitably lead to the change of output combination. Will the “university enrollment expansion”really cause the inhibition of the innovation efficiency in universities because of the increase of investment in talent training and the squeeze of investment in scientific research. If not, what are the reason and mechanisms? This paper provides an empirical evidence of innovation effect of “university enrollment expansion”.It enriches the research on the economic effect of “university enrollment expansion”and it can provide a basis for policy making to develop higher education in China.

After calculating the innovation efficiency with super efficiency DEA method on 31 provinces in mainland China and Hong Kong, Taiwan provinces of China from 1998 to 2014, this paper takes the innovation efficiency of each province as the dependent variable and the “university enrollment expansion” as the independent variable respectively. Through regression analysis with the method of difference-in-differences, it shows “higher education expansion” is conducive to innovation efficiency. According a series of robustness tests, the result is still robust.

Because “university enrollment expansion”can lead to increasing teaching staff, improving of teaching staff and increasing research input, and the three factors changed subsequently with “university enrollment expansion” all contribute to the innovation efficiency, this paper made an further study of impact mechanism test successively with the intermediary variables including the quantity and quality of teaching staff, the input of research. Further research shows that the reason why “university enrollment expansion” is conducive to innovation efficiency is that “university enrollment expansion” has led to the expansion of the teaching staff, the improvement of the quality of teachers, and the increasing of investment to scientific research.

Therefore, China should maintain a steady growth in university enrollment and increase teachers, boost research input meanwhile during the process of the “double first class” construction of the universities, which can promote the scale of higher education and the innovation efficiency at the same time.