Abstract: Agricultural machinery purchase subsidy is an important agrarian policy, its policy effect has been widely concerned by scholars. However, very few studies have discussed the spatiotemporal difference, agricultural machinery types difference and endogeneity of subsidy’s policy effect. The purpose of the present study is to make policy effect evaluation more accurately, and analyze the spatiotemporal difference and agricultural machinery types difference of policy effect. Different from existing studies, the present study uses a large sample collected from 15 089 observations in 3 287 households at 18 provinces from 2008 to 2018 by China agriculture research system (rapeseed) farmer fixed observation point and employs unbalance panel fixed effect model, panel high-dimensional fixed effects model, Box-Cox model, quantile regression model to calculate the differential policy effects between different year, topographic regions and types of agricultural machinery purchase subsidy on farmer’s agricultural machinery self-investment. In addition, instrumental variables fixed-effects panel-data models, Tobit fixed-effects panel-data models and Heckman sample selection models were used for the robust test. The result showed that 1) On the whole, agricultural machinery purchase subsidy had an obvious incentive effect, effectively promote farmer’s agricultural machinery self-investment, the marginal effect of agricultural machinery purchase subsidy on farmer’s agricultural machinery self-investment was 2.530 8. 2) The effect of subsidies varies significantly between plain and non-plain areas. Subsidy’s marginal effect in plain county was 1.408 5, subsidy’s marginal effect in hill and mountain county was 3.108 2. Subsidy policy was more effective in hill and mountain areas. 3) Generally, subsidy’s incentive effect fluctuated significantly between the years, crowding-out effect was showed in some years. The number of years in which the policy effect declined from the previous year was equal to the number of years in which it rosed from the previous year. 4) On the whole, the subsidy effect was enhanced with the increase of the value of agricultural machinery, and the policy effect was higher for large and medium-sized agricultural machinery. Accordingly, this paper suggested that: 1) In the future, agricultural machinery purchase subsidy should continue to implement. 2) Agricultural machinery purchase subsidy should tilt appropriately to non-plain areas and large and medium-sized agricultural machinery continually. Appropriate R&D subsidies can be given to agricultural machinery production enterprises to research and develop large and advanced machines and suit machines which used in hilly and mountainous areas. Encourage local governments to include large and advanced machines and machines which was suitable used in hilly and mountainous areas into the new agricultural machinery subsidy pilot catalogue timely. Accelerate the transformation and application for new machine products. 3) Adjust or improve the subsidy mode according to the implementation situation and agricultural mechanization development situation.