The intelligent Aim system of the Tear Bomb Emitter based on binocular stereo vision has been designed for the armored car equipped in our Armed Police Force. In this paper, according to the intrinsical feature of the background, the binocular stereo vision is chose to detect the forward distance between the bomb emitter and the crowd which the emitter needs to aim at. A new way which is based on integrating temporal information with spatial information has been presented. Then the forward distance was obtained according to the camera calibration, image processing, and error model. The error and measuring experiment shows that the percentage error is less than 2% and this method is feasible and effective.