As an important link between finance and environment, green financial policy is an important driving force to promote green innovation and realize green development. This paper uses the data of 935 manufacturing enterprises in China from 2007 to 2020 to test the impact of the implementation of the 2012 Green Credit Guidelines on green technology innovation based on the double difference model (DID), and conducts a heterogeneity analysis based on the nature of property rights and regional perspectives. The research shows that: ① after the implementation of the Green Credit Guidelines, thanks to the easing of financing constraints, the green innovation activities of clean manufacturing enterprises are more active; ② The green credit policy can more stimulate the increase of the number of green practical patents with low innovation content, short return period, low risk and reflecting the number of green innovations, but has no obvious effect on the increase of green innovation quality of manufacturing enterprises; ③ The green credit policy significantly improves the number of enterprises’ innovation in the western region, and has a strong incentive effect on the quality of enterprises’ innovation in the eastern region. The implementation of the green credit policy can ease the financing constraints of state-owned enterprises, thus bringing more obvious green technology innovation. Finally, this paper puts forward corresponding countermeasures and suggestions on how to better promote green technology innovation of enterprises in green finance.