Abstract: In this paper, the experimental and theoretical studies are presented of the contact electrification due to the ball-plate oblique impact, in which the ball and the plate have same chemical properties. Experimental results show that the ball can be electrified after impacting with a plate of the same chemical property as the ball, while the polarity of charge depends on the ball's material property. The magnitude of charge is related to the inclination angle of plate. With the increase of the inclination angle, the magnitude of charge first increases and then decreases. When the inclination angle reaches 50 degree, the magnitude of charge reaches its maximum value, which is 6-8 times of the magnitude of charge due to the direct impact. By a dynamic analysis of the ball-plate oblique impact, it is shown that the charge carried by the ball is highly related to the friction area between the ball and the plate in collision.