As a populous country, China needs to balance increasing total grain production with rationalizing input factors. How to improve grain production efficiency has become a highly concerned issue. This study uses provincial panel data (1978–2022) and a grain contribution rate model to calculate the provincial contributions of wheat, corn, rice, and legumes to national grain production. This paper analyzes the spatial distribution of grain crops in China, measures China's grain production efficiency and total factor productivity by using BCC, CCR and Malmquist index models, and analyzes the dynamic evolution trend of grain production efficiency since the reform and opening up by using nuclear density map. The empirical results show that: (1) Rice has the highest contribution rate to national grain crops (37.72%), with the three main grain crops in China distributed in a "V" shape. The middle and lower reaches of the Yangtze River and the Yellow-Huaihai Plain have the highest contributions to national grain production; (2) Grain production efficiency in China can be divided into three stages: a high-efficiency phase (1978–1998), a decline in efficiency due to a lack of scale efficiency (1998–2003), and an improvement phase (2003–2022), driven by pure technical and scale efficiency; (3) China's total factor productivity of grain showed a slight decline over the study period, with technological progress being a key driver of TFP growth.. To enhance grain production efficiency and ensure national food security, this study proposes region-specific suggestions tailored to variations in production efficiency.