Field plot experiments were conducted to investigate the root morphology and architecture traits,shoot biomass and seed yield of Huashuang 5 (HS5,conventional variety) andHuayouza 10 (HZ10,hybrid variety) (Brassica napus L.) under three cultivation methods including direct seeding (DS),direct transplanting (DT) and assistant transplanting with hoe (AT) during the whole growth stage.The results showed that root traits such as root dry weight,primary root length,root diameter and root volume under DS were more (better) than that under AT,the latter were more (better) than that under DT at the same growth stage with the same density and sowing time.Significant difference was existed in shoot biomass and seed yield among the three cultivation methods in the order of DS＞AT＞DT at the same growth stage.Root traits,shoot biomass and seed yield of HZ10 were better (higher) than that of HS5 at the same growth stage.Shoot biomass and seed yield were significantly correlated with root traits in oilseed rape under all the three cultivation methods.Varieties with greater root dry weight,thicker primary root and more 1st order lateral roots can absorb more nutrient and water,and produce more biomass and seed yield.Root breeding would play more important roles in improving seed yield of oilseed rape.