In order to promote the breeding and application of high nitrogen efficiency oilseed rape cultivars, the relationship between root activity, root absorbing surface, root volume and the number of lateral roots of different oilseed rape cultivars and nitrogen efficiency at different growth stages were studied by greenhouse experiments under different nitrogen levels. The result indicated that different nitrogen levels had significant effects on root morphologic and physiological properties during all growth stages, and all of those properties increased with the increase of nitrogen level. Under nitrogen application, except root vitality, the number of first-class lateral root at all growth stages, root volume and absorbing surface at seeding stage were significantly correlated with rape nitrogen efficiency. Under non-nitrogen application, the number of first-class lateral root and root activity at all growth stages, root volume and absorbing surface after seeding stage, were significantly correlated with rape nitrogen efficiency.