In connection with the characteristics of integral imaging three-dimensional display, the stereo depth of integral imaging three-dimensional display system has been calculated using the cognominal-points spacing in the adjacent elemental images. Through in-depth analyze the maximum and minimum stereo depth reproduced by the system, the reconstructing ability of stereo depth is presented. The results show that the lens array pitch and cognominal-points spacing have important influence on the stereo depth, and then the reconstructing ability of stereo depth in the integral imaging system is determined by the resolution of display device and the lens array pitch. On the basis of theoretical analysis, modulation of the stereo depth of system is realized with optical experiments through changing the cognominal-points spacing.