Human capital and agricultural production efficiency will show a nonlinear relationship due to the different land operation scale. The full play of human capital in production urges for a corresponding scale of operation,which could be illustrated by points below. (1) Human capital makes a significant negative effect on the efficiency of agricultural production when the size of farmland is small,and the influence of human capital becomes insignificant in the intermediate scale. In case of the large-scale operation,human capital shows a significant effect of promoting. (2) The limited size of farmland confines the reasonable rate of return from education investment,thus resulting in the selective transfer of the labor force. But an expanding scale of agricultural operation could convert the reduction of human capital. The agricultural production has to accept the “scissors” of city industries again because of the selective transfer of rural labor forces,which could be attributed to the limited scale of agricultural operation. The fundamental way to raise the efficiency of agricultural production in China is to break the land system,the household registration system and other institutional barriers to the expansion of farmland scale,and to promote the moderate scale management of agriculture.