Abstract: Agricultural mechanization has promoted the development of agricultural division and adjustment of planting structure. Based on a provincial panel data from 2001 to 2018 and applying the spatial Durbin model, this paper analyzed the spatial spillover effect of agricultural mechanization on planting structure. Results show that: 1) overall, the development of agricultural mechanization had some positive spatial spillover effects on the “tendency to grain production” in surrounding provinces, which was mainly manifested as large and medium-sized tractors in the cross-regional operation; 2) the rising price of local agricultural labor can promote the “tendency to grain production” of the surrounding provinces, while the urbanization development and the agroforestry expenditures had some negative effects; 3) the spatial spillover effect of agricultural mechanization was not significant from 2001 to 2003. However, after 2004, the spatial spillover effect of the total power of agricultural machinery and the power of large and medium-sized tractors was positive with an increasing trend. The initial spatial spillover effect of small tractors appeared since 2011; and 4) the spatial spillover effects of agricultural mechanization were different under different terrain endowments. The spatial spillover effects of the total power of agricultural machinery and the power of large and medium-sized tractors were positive in plain areas, while the spatial spillover effects of the total power of agricultural machinery and the power of small tractors were negative in hilly and mountainous areas. Consequently, this paper suggests: to strengthen the regional coordination of agricultural machinery, to promote measures of farmland construction suitable for mechanization, and to accelerate the socialized service of agricultural machinery.