Large-scale farmers are the important contributors of grain production in China. Under the background of rigid resource constraints and rising production costs, improving the technical efficiency of large-scale grain-production farmers is the fundamental way to guarantee the food security and increase the peasant's income of our country. Based on the survey data of 674 large-scale grain-production farmers in Heilongjiang Province, and using the SBM super efficiency DEA model, this study empirically examined the technical efficiency, the distribution of efficiency, the decomposition of efficiency and the slack variables of input. Furthermore, this paper analyzed the main factors influencing the technical efficiency by using the Tobit regression mode. The conclusions are listed as: Firstly, the average comprehensive technical efficiency, pure technical efficiency and scale efficiency are 0.545, 0.635 and 0.871 respectively. The average comprehensive technical efficiency is not high, and the main reason is the low pure technical efficiency. Secondly, the land management scale has a U-shaped curve relationship with the comprehensive technical efficiency, the same relationship as pure technical efficiency. Thirdly, the vast majority of large-scale grain-production farmers have redundancy in the input factors, and the improvement degree of input factors from high to low is land rent, flowing cost, fixed cost and labor cost. Finally, the factors such as the age, total cultivated land, the number of farm population, the number of soil blocks, the largest plot area, the proportion of farmland, the state of irrigation facilities, the way to irrigate, the term of land circulation contract and the availability of formal loans have significant impacts on the technical efficiency of large grain farmers.