34 medical college students and 26 patients with primary hypertension were served as the subjects on low sodium salt diet for 4 weeks. Before and after the experiment, serum and urinary sodium and potassium, as well as blood presure, pulse rate, and body weight were measured. During the testing period, calorie and protein were supplied sufficiently and the salt content in their common diet taken was restricted strictly. The results showed that the serum sodium decreased, potassium increased at the end of the experiment, but the changes were all within the physiological permissible limits. On the contrary, urinary sodium increased, potassium decreased and the Na/K dropped markedly, body weight increased slightly in healthy subjects and decreased by 1.0-3.0kg in patients with hypertension. The blood pressure, both systolic and diastolic, was decreased but no change in the pulse rate was observed.It was obvious that in the subjects on common salt diet, the body sodium was high and potassium low, otherwise on low sodium salt diet, such situation might be improved, and the high blood pressure could also be ameliorated in the type Ⅰ and Ⅱ of hypertension.