A systematic investigation of the impacts of the functional transformation of farmland utilization in northeast China on grain production is helpful to hold the relationship between farmland and grains from the national level to provide scientific reference for the realization of agricultural modernization, grain security, and high-quality development in China. Based on a provincial panel data from 2011 to 2020, this paper analyzed the functional transformation characteristics of farmland utilization in northeast China and its function mechanism affecting national grain security by the entropy weight method and the double fixed model. Results show that: China""s grain security level was on the rise from 2011 to 2020, and the transformation of farmland utilization function in northeast China effectively enabled the national grain security. In the regional heterogeneity study, the grain security guarantee effects of farmland utilization functional transformation in Liaoning and Heilongjiang Provinces were more obvious, but the function channel of Jilin Province needed to be unblocked. In the dimensional heterogeneity study, the farmland utilization functional transformation in northeast China mainly guaranteed China""s grain security by promoting grain quantity security and grain economic security, but the effect of grain ecological quality assurance was not obvious. Therefore, to make the northeast region farmland utilization functional transformation to better promote national grain security, this paper suggests: providing economic subsidies for farmland utilization and grain production in northeast China, formulating the strategy of farmland utilization functional transformation in northeast China according to local conditions, and building a "high-quality food project" oriented by ecological quality.