A method for merging separated pixel blocks into an integral image of an object is provided. The method performs binary image processing on an obtained image to obtain a binary image, finds pixel blocks in the binary image whose area is greater than a first preset value, and stores a position and a size of each found pixel block in a data structure. The method further merges two pixel blocks in the data structure if a distance between the two pixel blocks is less than a second preset value, so as to generate the integral image of the object.