Based on the theoretical analysis of the impact of free farmland transfer on grain production efficiency,this paper empirically tests the effect and influence mechanism by using Inverse Probability Weights (IPW) method.The main findings are as follows:Unlike the paid farmland transfer,the free farmland transfer is a non-market behavior based on the ethical relationship of family and community.After solving the sample selection bias,free farmland transfer fails to improve grain production efficiency.The reason is that the absence of transfer rents makes it easier to weaken the signal function of factor price and the willingness of farmers to improve production,which in turn prevents them from making the same improvement in long-term agricultural investment and avoiding land fragmentation as the farmers who are paid to transfer their farmland.This negative effect is more prominent with the group of farmers whose household heads are younger or better educated,who have more agricultural subsidies or lower marketization level,and whose scale of transferred farmland is small or the duration is unclear.In the long run,with the continuous development of rural collective economy and new agricultural business entities,the free farmland transfer may continue to decrease.But at the same time,based on respecting and affirming the actual choice and value of free farmland transfer,all localities should identify and plan the specific direction of large-scale operation according to the specific situation of various regions.