Abstract: In order to indicate the dry matter accumulation and the characteristics of the distribution, absorption and accumulation of selenium in Brassica napus, this paper used the field plot experiment and tested the dry matter accumulation and the content of selenium of different organs at different periods in Brassica napus. The results showed that, the dry matter accumulation quantity of Brassica napus was increased rapidly at harvest period and reached the maximum, the value was 48765.20 kg/hm2. The change of dry matter’s accumulation quantity and the proportion in different organs was different. The dry matter’s accumulation quantity in roots and stems showed a rising trend and reached the maximum at harvest period, the values were 3082.20 kg/hm2, 15138.93 kg/hm2, but the dry matter’s proportion showed a descending trend; the dry matter’s accumulation quantity in leaves showed a descending trend; the dry matter’s accumulation quantity in seeds and siligue shells showed a rising trend and reached the maximum at harvest period, the values were 14922.60 kg/hm2, 15621.47 kg/hm2. Selenium’s accumulation of Brassica napus reached its maximum at harvest period, the value was 6.94 g/hm2. Selenium’s content of roots, stems, leaves, seeds, siligue shells in Brassica napus reached its maximum at siligue shells period, the values were 0.16 mg/kg, 0.26 mg/kg, 0.60 mg/kg, 0.21 mg/kg, 0.34 mg/kg. Selenium’s accumulation of roots, stems, leaves, seeds, siligue shells in Brassica napus reached their maximum at siligue shells period, siligue shells period, seedling period, harvest period, harvest period, the values were 0.24 g/hm2, 1.45 g/hm2, 0.32 g/hm2, 1.66 g/hm2, 3.84 g/hm2. The order of selenium’s content and accumulation in different organs of Brassica napus was siligue shells > seeds > stems > roots at harvest time. Selenium’s distribution center was different at different growth periods, the distribution center was nutritive organs at earlier growth period, and the distribution center was reproductive organs at later growth period. Then, selenium’s proper application should be used at later growth period.