To realize the harmless treatment and complete resource utilization of livestock manure, the Chinese government continues to promote the outsourcing livestock manure (OLM) services. Exploring OLM's impacts on farmers' incomes is of great significance to evaluate and improve the socialized service system. However, the economic effects of OLM still lack empirical support. This study collected data from 600 pig farmers and applied the ordinary least squares (OLS) method, endogenous switching regression, quantile regression, and mediation effect methods to analyze the influence mechanism of OLM on farmers' incomes. The results revealed that OLM significantly increases farmers' incomes, with those who adopt outsourcing services earning approximately 74,800 yuan more than those who do not. The main reason OLM has an income increasing effect is that it can promote large-scale farming and farming efficiency. As farmers' incomes grow, the income increasing effect of OLM has a clear inverted U shape, with the maximum effect occurring at the 50% income quantile. Meanwhile, with the increase of outsourcing degrees and expansion of the farming scale, the income increasing effect of OLM is also enhanced. After considering geographical characteristics, the analysis showed that OLM had a better income increasing effect in farms located between 500 and 1000 m above sea level. In conclusion, this study reveals the application performance of outsourced services in livestock manure treatment processing, which can help government departments to continuously promote and drive the recycling of livestock waste resources.