Abstract: It is more precise to characterize the repellency of the fabric by contact angle.The method of measuring the contact angles between a droplet and fabric is one of the most commonly methods,whereas hypsometry and goniometry are most commonly used methods in the measurement of an angle.It is found through actual tests that these two methods results in larger measurement error,and its cause remains unknown yet.In this paper,the principle and error of these two methods were analyzed and compared theoretically.Meanwhile,the measurement error of contact angles caused by the measurement error of droplet height,the bottom diameter of droplet and the turning error of protractor were discussed.Verification experiments were performed and the results obtained are coincident with the theory.Finally,hypsometry is proved to be more precise,faster and more convenient.