An image processing system includes a dual lens module and a processor. The dual lens module captures a pair of images. The processor generates a depth map of the pair of images. The processor generates a pixel depth distribution histogram according to the depth map. The processor calculates a pixel depth mean and a pixel depth variance according to the pixel depth distribution histogram. The processor determines whether the pixel depth mean is within a distance range and determines whether the pixel depth variance is smaller than a first threshold or larger than a second threshold, so as to determine that the dual lens module is situated in a normal state or an abnormal state.