Nitrogen (N) is one of the essential macronutrients for plant growth and development.Large amount of N fertilizers are required for rapeseed (Brassica napus) production,while the N use efficiency (NUE) of B. napus is very low.Results of previous researches showed that there was large genotypic variation for NUE among B. napus cultivars.Compared with low-N efficiency genotypes,high-N efficiency genotypes had advantages in N uptake,transportation,metabolism,photosynthesis and remobilization etc.The expression level of genes involved in processes including nitrate transporters,ammonium transporters,genes encoding enzymes involved in N metabolism was significantly affected by N availability.Significant differences were found in the expression level of genes involved in N efficiency between low-N efficiency cultivars and high-N efficiency cultivars.This paper reviewed the progresses in physiological basis and molecular mechanism in N efficiency of B. napus from two aspects including genotypic variation of NUE among different B.napus cultivars,and physiological and molecular basis of B.napus with N efficiency.