Specialized and innovative enterprises occupy an important position in the industrial chain. Their competitive advantages are based on long-term deep cultivation and technological accumulation, and invention patents are crucial to the further development of enterprises. The selection and cultivation of little giant enterprises began in 2019, indicating that the development of specialized and innovative enterprises has been placed in a significant position. The invention patent is the short board of specialized and innovative enterprises for a long time. It is urgent to explore the effect of policy implementation on invention patent through in-depth empirical research. We collect patent data and analyze the policy effect with difference-in-difference method. The results reveal that the policy has a promoting effect on invention patent application, and the promoting effect is more significant in discrete and patent intensive industries. However, limited by scale strength and innovation resources, the number of invention patent applications of little giant is still low. Therefore, it is necessary to promote the selection and cultivation of little giants, strengthen the follow-up assessment for selected enterprises, and continue supporting their invention patent application.