Several problems in the study of the population supporting capacity of land resources are discussed in this paper. The problems are the understanding of definition, the calculating of land productivity and crop yield, the evaluating of land resources, and the adjusting of land use structure.How to define and understand the population supporting capacity of land resources is the key in the study. A specified land evaluation for the study is the necessary foundation for the land productivity calculating and the land use structure adjusting. The predicted crop yield based on economic statistics can not represent land productivity. There are also some problems in crop yield calculated by the method of AEZ.