China is actively expanding its imports. Under the background of increasing trade opportunities for micro and small enterprises and carrying forward the innovation-driven development strategy, this paper explores the effect of import on firm innovation using data from China Micro and Small Enterprise Survey. The results show that the import of micro and small enterprises plays a significant role in promoting innovation. This is mainly obtained by small enterprises and processing trade enterprises. More specifically, the innovation effect of import of micro and small enterprises is mainly reflected by the promotion of intermediate import to the independent R&D, the impact on technology import is not significant. The use of imported intermediates is good for new products or technology, while import of final products spur other innovations. Using the intermediary effect analysis model and simultaneous equations models, the test of conduction mechanism shows that import of micro and small enterprises increase firm innovation by raising the consciousness of innovation and improving the innovation resources.