A crucial parameter for the successes of stereo matching algorithms is the disparity search range estimation.It is necessary to estimate the disparity search range between stereo pairs automatically in real time systems.A dual-mode camera which can be used to take stereo images or depth maps is developed in our work.Under the constraint of the depth map with the same spatial resolution as the stereo pairs,expected disparity of each pixel is limited within a narrow search range.For images captured in our lab,the process of stereo matching is sped up more than 3 times and the error percentage is reduced by 2% compared with the method that estimates the minimal and maximal disparity between stereo pairs.