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For the traditional slant method in the determination of potato static friction coefficient, there are problems of efficiency and low precision, based on the principle of water gravity potato static friction coefficient determination, by accurately controlling the weight of water to determine the static friction of potato, and then calculate the static friction coefficient, according to which the potato static friction coefficient determination instrument was developed. The static friction coefficient of Long potato 10 varieties commonly grown in Gansu was determined. The results showed that the static friction coefficient between Long potato 10 and steel plate with soil was 0.420, the static friction coefficient between it and plastic plate was 0.496, the static friction coefficient between Long potato 10 was 0.442;without soil, the static friction coefficient between Long potato 10 and steel plate was 0.455, the static friction coefficient between it and plastic plate was 0.526, the static friction coefficient between Long potato 10 was 0.483. This showed that the static friction coefficient of potato with soil was smaller than that of potato without soil, and the static friction coefficient from large to small was as follows: between potato and plastic plate, between potato, between potato and No.45 steel plate. In order to further verify the reliability of the gravity method, the potato collapse stacking angle simulation and test for Long potato 10 were done. It was found that the pile-up angle formed by potato without soil under the condition of gravity method was close to the test results, and its relative error was 1.04%, relative error with the test results of the pile-up angle formed by potato without soil under the condition of slant method was 7.73%;the pile-up angle formed by potato with soil under the condition of slant method was close to the test results, and the relative error was 0.37%, and the relative error of pile-up angle under the condition of gravity method was 4.31%. In addition, the gravity method can determine the static friction coefficient between potatoes. The gravity method was superior to the slope method in determining the static friction coefficient of potatoes.