Tennis players often used slice backhand in tennis matches. The ball speed plays an important role when the players perform a good slice. The objectives of this study were to determine (1) the correlation between (A) the ball speed and incident angle, (B) the ball speed and rebound angle, (C) the ball speed and the angle difference, as well as (2) the difference of (A) incident angle, (B) rebound angle, (C) the angle difference between the fast ball and slow ball. The subjects of this study were 5 males who rank top 15 in domestic. Ball projector is used to control the ball speed and speed gun, to measure the return speed. The ball trajectory was recorded in target area by high speed video camera. The results showed that the significant correlation were found between (A) the ball speed and incident angle, (B) the ball speed and rebound angle, (C) the ball speed and the angle difference. (p＜0.01). It showed that the slice backhand with faster ball speed has less incident angle, rebound angle. There is significant difference between the fast ball and slow ball with backspin in (A) incident angle, (B) rebound angle, (C) difference. This result indicates that faster ball speed will make the ball skid and remain low when it bounces. The key movements during the backhand forward swing are forward rotation of the upper arm followed by extension of the forearm at the elbow. The elite tennis players should plays an important role in the development of racket speed in the backhand groundstroke. In conclusion, the tennis players should improve control ability, and more importantly, increase the ball speed in tennis drill.