Local government investment can influence renewable energy technology innovation (RETI). Based on the panel data of 30 provinces in China from 2007 to 2019, this paper uses fixed effect models, partial linear generalized function coefficient models, and other methods to test the impact of local government investment preferences (LGIP) on RETI. The results are: (1) Productive investment preferences significantly inhibit RETI. (2) The impact of productive investment preferences on RETI is heterogeneous across economic development stages and regions. (3) With economic growth, the negative impact of productive investment preferences on RETI gradually decreases. The findings suggest that local governments should adjust investment patterns and appropriately reduce productive investment to improve RETI.