In order to extract the information in the complex image of the visual prosthesis more accurate, a new focus subimage extraction method based the visual saliency and new edge detection algorithm fusing multiscale information of image edge strength are proposed. Firstly, it uses the GB method to calculate the image saliency map, and applying the double thresholding on the saliency map, the initial segmentation is modified by the morphology processing and the focus subimage is obtained finally. Secondly, considering the deficiencies of traditional single scale edge detection, the edge detection based on the fusion information of the mutiscale Sobel operators is proposed. The proposed complex image processing strategy not only simplifies the complexity of the encoding image information, but also improves the noise robustness of edge extraction algorithm.