The phenomenon of farmland abandonment has received widespread attention in the academic community，but there is still a lack of effective quantitative assessment of the impact of farmland abandonment on food production.This paper integrates farmland abandonment and food production into a unified analytical framework and uses the data of China Rural Household Tracking Survey （CRHPS） in 2017 to conduct an empirical test. It is found that there is a threshold effect of farmland abandonment on grain output，that is，farmland abandonment needs to reach a certain scale to affect grain output. The mechanism analysis indicates that the nonlinear relationship between farmland abandonment and grain output is caused by the quality difference of abandoned plots and the change in factor allocation level of remaining plots.Small-scale farmland abandonment mainly involves low-quality plots，resulting in relatively small food loss.At the same time， abandoning low-quality plots will also improve the factor allocation level on the remaining plots，leading to increased grain output，thereby partially offsetting the grain loss.However，this increase in production will gradually diminish as the size of off-farm employment increases. Further analysis shows that introducing agricultural technology and enhancing human capital level can effectively mitigate the adverse impact of agricultural land abandonment on grain output.The paper emphasizes that current farmland abandonment primarily targets inferior land with low yield and does not pose a significant threat to food security.In addition，the necessity for using administrative measures to promote the re-cultivation of low-quality land for grain cultivation should be carefully considered. In contrast，measures such as converting abandoned land to forests （or grasslands） or planting other economic crops may be more feasible and potentially advantageous.