As a new form of trade and business model, digital service trade is becoming more and more important in promoting the development of national innovation. Based on the panel data of 66 countries in the world in 2019, the effect of digital service trade on national innovation ability is carried out, and the role of income gap is discussed, and the heterogeneity analysis of national samples based on different economic development levels is carried out. The results show that digital service trade has a significant positive effect on the improvement of national innovation ability. The income gap plays a partial intermediary role between the two. The development of digital service trade in high-income countries is more important to the ability of national innovation, while middle-income countries are limited to the stage of economic development, and a certain degree of income gap income gap can improve the ability of national innovation. To this end, the middle-income countries, including China, need to reform the distribution of income, promote the development of digital service trade and income gap, and promote the promotion of national innovation ability.