The effects of foliar application of Selenium(Se)on rice,soybean,maize and wheat were analyzed.Result showed that the original Se content was the highest in soybean and the lowest in maize,the order was soybean>wheat>rice>maize.After foliar application of Se with same concentration,the grain Se content increased obviously in all the crops,and grain Se content positively correlated with the concentration of Se.In wheat and rice it increased more than other crops,and maize had the lowest Se content,and all the grain Se content was within the range of safe selenium.The range of Se concentration was about 11.25~22.50 g·hm-2,which could meet the needs of the residents in low Se region.The best foliar application period of Se for rice was in the later blooming stage,for maize was in the tasseling stage,for soybean was in the first flowering stage,and for wheat was in the pregnancy stage.Humic acid Se reduced the toxicity of high concentration of Se to crops and it was more safely in production.