Stereoscopic image quality assessment is an effective way to evaluate the performance of stereoscopic video system. However, how to utilize human visual characteristics in quality assessment is still an unsolved issue. In this paper, an objective stereoscopic image quality assessment method is proposed based on perceptual significance. Firstly, by analyzing the effects of visual saliency and distortion on perceptual quality, we construct perceptual significance model of stereoscopic images. Then, we separate the stereoscopic image into four types of regions: salient distortion region, salient non-distortion region, non-salient distortion region and non-salient non-distortion region, and evaluate them independently. Finally, all evaluation results are integrated into an overall score. Experimental results show that the proposed method can achieve higher consistency with the subjective assessment of stereoscopic images and effectively reflect human visual system.