1) Germplasm resources are relatively scarce and the foundation is narrow. At present, there are four available breeding populations, but IHO has poor agronomy, so only three varieties BHO, ASK and RYD3 can be directly used for breeding.2) There is a contradiction between high oil and high yield and high quality. Corn oil mainly exists in germ, and the selection of high oil content will easily lead to the decrease of grain quality. Therefore, there is a certain contradiction between high oil content and high yield.