Abstract: The narrow genetic background is the first constraint factor of maize (Zea mays L.). It is essential to broaden the genetic diversity of maize resources through recurrent selection. Yunlun No. 1 germplasm popula?tion derived from the mixed pollination after crossing the U.S. firm rod BSSS population with the population composed of eight inbred lines with Chinese Reid blood. After conducting three mixed selection，Chang 7-2 was used as test varieties to analyze the combining ability of the Yunlun No. 1 germplasm population’s yield traits. The results show that the population has rich genetic variation and there are significant differences among the individual plants of population. Twenty excellent selfing plants are selected from 138 test varieties as a new round of reincarnation parent correspondingly. It is expected that the yield combining ability of the new round of composite population will increase by 11.6%, milking and dehydration rate will be superior to the control and agronomic traits will also be improved accordingly.