Abstract: Alkaline potassium persulfate digestion UV spectrophotometric method,as a standard method from HJ636-2012,is facing with many problems,one of which is that potassium persulfate is difficult to dissolve. The research compared sodium persulfate with potassium persulfate by using them in standard curve and twelve nitrogen standard solutions' digestion. According to the experiment,it was found that the standard curve with sodium persulfate had a low blank value. There was no significant difference about twelve nitrogen standard solutions. Therefore,using sodium persulfate to replace potassium persulfate in total nitrogen's measure is feasible.