Abstract: Selenium is indispensable to human being and domestic animals and it's an important component part of GSH-Px.Se deficiency or excess of Se in the environment has been found to be associated with a variety of diseases in humans and domestic animals.Qinghai plateau is belongs to region with Se deficiency.Selenium application is an effective method to rectify the deficient selenium state of human being and domestic animals.In this experiment,selenium was sprayed on the leaves of carrot to examine the effect of Se on Se uptake and transform,yield and quality of carrot.This experiment consisted of 6 treatments: 0,0.5,10.0,50.0,100.0 and 500.0 mg/kg of Se as Na2SeO3.The results showed that foliage application of selenium significantly increased the Se content of all morphology in carrot.With the(increment) of application rate of Se,the transformation rate of organic selenium went up.Total selenium and organic selenium reach the peak at the highest concentration treatment of 500 mg/kg,which were 15.9 and 26.6 times of that of control respectively.Se application decreased the carrot yield compared with control,but it did reach the statistical significant.As for the quality of carrot,using a special concentration of selenium on the carrot increased total sugar,carotin,crude-fibre content and the absorption of calcium,magnesium,iron and potassium in carrot to different extents.However,the vitamin C content decreased and the absorption of phosphorus was unconformity.Comprehensive considering the effects of selenium application on the selenium content,yields and various quality factors of carrot,as well as food safety for human and livestock health,the appropriate application rate of Se should not be more than 1.0 mg/kg.