Abstract: During the key promotional period for the high-quality development of the grain industry, it is an imperative trend to adjust the planting structure and to improve the total factor productivity (TFP) of grains. Based on a panel data collected from the prefecture-level cities in the three Northeast provinces of China between 2001 and 2016, this paper calculated the TFP of grains by the DEA-Malmquist index method and explored the influences of corn planting structure on its TFP by the spatial SAC model. Results show that the average increase rate of TFP in the three Northeast provinces of China was 1.1 percent each year, the technical efficiency and the technological progress increased by 0.5 percent and 0.6 percent, respectively. However, the increase of grain TFP showed a steady declining trend, while the technological progress growth fell under a “homogenous path”. The expansion in planting area and the rising planting proportion of corn will lead to an “efficiency loss”, which is predicted to further lower the grain TFP. The influential path of corn planting structure on the grain TFP is realized jointly by technical efficiency and technological progress. The influence on technical efficiency is achieved only through the scale efficiency. In summary, this paper draws the following conclusions that the adjustment of corn planting structure could improve the grain TFP and it could also provide a solid foundation for the high-quality development of the grain industry.