The soil available magnesium（Mg） is typically low in the main producing area of rapeseed. In recent years,Mg deficiency is becoming a potential factor limiting rapeseed yield due to the unbalance between large removal of Mg under high productivity cropping system and less input under current nutrient management that prioritizing the application of nitrogen,phosphorus and potassium. On the purpose to comprehensively evaluate the soil Mg status and the effects of Mg application on seed yield,the present review summarized the main progress of Mg nutrition research in rapeseed plants. It is indicated that rapeseed requires 20-40 kg/hm2 Mg for better growth and a large area of soils in the main producing area lack sufficient available Mg (the average value of soil available Mg is 225.7 mg/kg,of which 53.7% of the soils is less than 200.0 mg/kg,in a state of Mg deficiency). The application of Mg fertilizer greatly improves seed yield by more than 15%. Mg is proposed to be the fifth essential element following nitrogen,phosphorus,potassium and boron,and to be supplemented by fertilization. It will provide suggestions for the scientific management of Mg fertilizer in winter rapeseed production. For better rapeseed production,we also propose recommendations for Mg fertilizer.