An image encryption method based on laser speckle sub region is proposed. Many sub regions are extracted from random laser speckle images,and each sub region is scanned for different random sequences by using SCAN language. Multiple sequences are added,and their modules are calculated to form new sequences,which is made bit-wise exclusive or implement encryption with original images to be encrypted. It proves that the method is feasible and safe by analyzing encryption effect,key space,key sensitivity and statistical feature of Lena image. The unpredictability of the speckle image reduces the possibility of being decoded.