Abstract:In the process of China""s reform and opening up, the policy of development zones has played an indispensable and important role in promoting China""s economic development and technological progress, and its role in promoting city innovation has been unanimously recognized by the academic community. However, it is unclear whether the problem of industry-city separation existing in the construction process of development zones has been improved with development, and whether the degree of industry-city integration affects the role of development zones on urban innovation. Based on this question, this paper uses a quasi-natural experiment of upgrading economic and technological development zones from provincial to national level during the period 2009-2019, and verifies the mechanism of the effect of upgrading development zones on urban innovation from the perspective of city-industry integration using a double difference method. The study shows that the upgrading of development zones can effectively promote the quantity and quality of innovation in the cities in which they are located, and passes a series of robustness tests; the city-industry integration is an important reason for the increase in the quantity and quality of innovation in the cities in which the zones are upgraded, mainly through the promotion of service sharing, factor flow and collaborative innovation. Further, depending on the geographical location and development level, the quantitative and qualitative effects of upgrading of development zones vary, with positive effects on the innovation level of cities in central, western and northeastern regions, except in the east, and a significant incentive effect on innovation-following cities. The policy of upgrading development zones also has a linear "superposition effect", with the number of upgrades increasing to boost the level of urban innovation.