The invention discloses a method for testing the fatigue performances of a swinging arm, and the method comprises the following steps: a, respectively installing a connecting shaft and a ball pin on a swinging arm installation seat and a ball pin installation seat; b, installing the swinging arm installation seat and the ball pin installation seat on a test bench; c, enabling the front end of a test torsion rod to be connected with a connecting support, enabling the tail end of the test torsion rod to be connected with a spline sleeve, and enabling the spline sleeve to be installed on a torsion rod fatigue testing machine; d, enabling a tested swinging arm to be installed on the test bench, enabling the connecting support to be connected with the tested swinging arm, and enabling the tested swinging arm to be pressed on the ball pin; e, applying a circular load to the test torsion rod through the fatigue testing machine, and transmitting the circular load to the tested swinging arm through the test torsion rod; f, judging that the fatigue performances are qualified if there is no crack when the number of circulating times reaches a certain value, or judging that the fatigue performances are not qualified if there is crack. Compared with the prior art, the method employs a simple structure which is low in manufacture cost and very convenient to use, and can accurately test the fatigue performance of the tested swinging arm.