Abstract: Under the background of the increasingly serious agricultural non-point source pollution, it is of great theoretical and practical significance to study the impacts of farmland management scale on the reduction of chemical fertilizer application for the realization of green and sustainable agricultural development in China. Based on a survey data of 769 rice farmers in 8 counties of Jiangxi Province, this paper explored the internal mechanism between the scale of farmland management and the reduction of chemical fertilizer by the two-stage least squares method (Ⅳ-2SLS) with instrumental variables. Results show that the management scale of farmland had a significant impact on the fertilizer application intensity, and the relationship between them was a "U" type, with the moderate scale of 4.60 hm², that is, the fertilizer application intensity decreased first with the expansion of the management scale, and then increased after reaching the moderate scale. The inflow of farmland and the quality of farmland have significantly enhanced the regulatory effect of the management scale on the reduction of chemical fertilizer. Further research found that the scale of farmland management of the new and old generation of farmers had a significant impact on the effect of fertilizer reduction, but there was no significant difference between the new and old generation of farmers; The scale of farmland management in hilly and mountainous areas has a significant impact on fertilizer application intensity, while that in plain areas is not significant. The scale of farmland management of two part-time households has a significant impact on the effect of reducing fertilizer application, while that of one part-time household is not significant. Therefore, the government should further actively promote the appropriate farmland transfer, transform agricultural infrastructure, build high standard farmland, improve the quality of farmland and the level of large-scale operation, and take different measures to protect farmland for different types of farmers and areas with different natural conditions.