The invention relates to a testing device for a ball eye flexural vibration fatigue characteristic in a power transmission line, belonging to the technical field of detection of power transmission line hardware, wherein a motor output shaft is linked with a bearing, and an eccentric shaft top block is arranged at the end part of the bearing. An upper air cylinder and a lower air cylinder are fixed on a device bracket, an upper sliding block and a lower sliding block are arranged at end parts of a mandril of the upper air cylinder and a mandril of the lower air cylinder, test sample colliding blocks are fixedly arranged on end faces of the upper sliding block and the lower sliding block, and a to-be-tested ball eye is arranged between the two test sample colliding blocks. The eccentric shaft top block at the end part of the bearing is arranged at one side of a test sample chuck. An oil cylinder is arranged at the other side of the test sample chuck, a piston of the oil cylinder is connected with a to-be-tested ball, and the end part of the ball of the to-be-tested ball eye is embedded in a groove of the test sample chuck. The testing device can be used for applying an impaction force and a tensioning force to the ball eye, and simulating a use tension of an actual line and use states under various complicated use conditions; various testing data of service life and fatigue resistance of the ball eye can be theoretically obtained within the shortest time.