The oil content of maize kernel is usually heritable,and oil content was controlled by many micro-effected genes,represent level range from 0.3 to 0.6 percent.Through the methods of the commix selection or the recurrent selection,some high oil groups and inbred lines were selected.It is the main methods to improve oil content of maize by selecting high oil inbred lines and second cycle lines using high heritability of high oil content in maize kernel.