Abstract: Yundan 21 is a maize hybrid with inbred line WD03 as parent, inbred line N75 as parent. The breeding process and characteristics of Yundan 21 parent inbred lines were introduced, and the breeding techniques of parent inbred lines were summarized. The technical measures of high-yield seed production were summarized from the selection of base, scientific population structure and sowing time. The results showed that the suitable seed production density was 75 000~90 000 plants/hm², the ratio of parents was 1∶4,the sowing time was the same period.

Key words: Yundan 21, WD03, N75, parent breeding, high-yield seed production technology