The new maize variety Shaandan 21 (Shaandan 9704) was bred by the male Wu 464 and the female K22 in Maize Institution, Northwest Sci-Tech University of Agriculture and Forestry in 1997. In 2000~2002, the regional test, product test results showed the characteristic of high-stable yield, early mature, disease resistance, good adaptation. The adaptive planting areas were the middle and west parts of Guanzhong plain, Shaanxi province. The optimum desnity range was 45000~50000 seeding / ha. It has been authorized by Crop Authorization Committee of Shaanxi Province in March 2003 and was named Shaandan 21.