Effective reduction of pesticide application in agricultural production is crucial for improving the quality of agricultural products and realizing high-quality agricultural development.Based on two-year mixed cross-section data from the China Land Economic Survey （CLES） in 2020 and 2021， this paper explores the effect of outsourcing of pesticide application service on pesticide reduction and its mechanism.The findings reveal three key points：first，agricultural outsourcing service significantly reduced pesticide application.This finding remains robust after adjusting sample combinations，putting emphasis on rice farmer，dealing with selectivity bias and considering endogeneity.Second，mechanism tests demonstrate that outsourcing of agricultural service could reduce pesticide application through labor constraint alleviation and scale effect realization，while the hypothesized pathway of pesticide variety substitution was not verified.Third，contextual analysis indicates that the intensity of front-end outsourcing amplifies the pesticide-reduction effect of application outsourcing on pesticide reduction，while the intensity of diseases and pests in the previous year weakens the pesticide reduction effect of application outsourcing. This paper indicates that application service outsourcing plays a positive role in promoting pesticide reduction，and it is necessary to accelerate the adoption rate of application service outsourcing，so as to further help promote the strategy of “dual reduction”.