Using pot-cultivated Pakchoi var.Shanghaiqing,effect of urea applying rate on the Pakchoi output,content of nitrate,nitrate reductase activity,and the content of nitric in Pakchoi was studied.The result showed that the Pakchoi output,content of nitrate,nitrate reductase activity,and the content of nitric in Pakchoi increased with the increase of urea consumption.Compared with the control,the difference was extremely significantly.Comprehensively considering the increasing of the output of Pakchoi and the decreasing of the nitrate pollution,the proper urea consumption should be 30～33.7kg/667m².