Using a sample of 548 households in 48 Chinese villages,this paper studies the relationship between agricultural productivity and farm size.Our results show regularity the inverse relationship between land productivity and farm size in China rural household foodstuff production,the GMM estimation about the elasticity coefficient of the plantation area on the output per mu is 0.58;In the provinces which the farm size are larger the elasticity coefficient are bigger.After by means of IV estimation and fixed effect models provided with controlling the select bias and heterogeneity of land quality,the inverse relationship can’t be explained by pure statistics viewpoints and self-selection.