Agricultural machinery input (AMI) plays a crucial role in promoting agricultural green development and advancing agricultural modernization. Based on panel data from 130 cities in the Yangtze River Economic Belt (YREB) from 2013 to 2022, we employ the spatial Durbin model for empirical analysis and draws the following. (1) The AMI in the YREB promotes local agricultural green production efficiency (AGPE) but inhibits that of neighboring areas. Moreover, with the increase in AMI, the impacts exhibit an "inverted U-shaped" and "U-shaped" trend, respectively. (2) The positive direct impact of AMI on AGPE is smaller than its negative spillover effect. (3) The expansion of agricultural operation scale (AOS) and the increase in grain yield per unit area (GYPUA) facilitate AMI in promoting local AGPE. Moreover, the expansion of AOS mitigates the negative impact of AMI on the AGPE of neighboring areas. (4) Notably, a threshold effect exists in the relationship between AMI and AGPE for both AOS and GYPUA. When AOS and GYPUA exceed certain threshold values, the promoting effect of AMI on AGPE is further strengthened. (5) Heterogeneity analysis shows that AMI in the upper, middle, and lower reaches of the YREB exhibits distinct patterns. Based on these findings, the following policy recommendations are proposed: establishing an agricultural machinery information service platform, strengthening vocational education and training for farmers, increasing support for energy-efficient and environmentally friendly agricultural machinery, and promoting land transfer.