1. A moving object segmentation method used by a detecting system, the detecting system comprising: a frame generator for periodically picturing a scene according to a predetermined period to generate a plurality of image frames, each image frame comprising a plurality of pixels, each pixel comprising at least a reference parameter for describing characteristics of the pixel; and a calculating device for detecting moving objects moving inside the scene according to a first image frame and a second image frame generated from the frame generator, the first image frame being generated prior to the second image frame by an interval corresponding to the predetermined period; the moving object segmentation method comprising: (a)comparing the reference parameter of one pixel in the first image frame with the reference parameter of the same pixel in the second image frame to generate a corresponding difference value; (b)comparing each difference value with a first threshold value and a second threshold value, the first threshold value being greater than the second threshold value, generating a plurality of first contours according to the pixels which are adjacent to each other and each having the difference value greater than the first threshold value, and generating a plurality of second contours according to the pixels which are adjacent to each other and each having the difference value greater than the second threshold value; (c)selecting second contours that overlap the first contours for establishing a corresponding first moving area, the first moving area comprising every pixel associated with the selected second contours; (d)determining whether the pixels outside the first moving area in the second image frame are registered as background pixels; and (e)comparing the reference parameter of the background pixel in the second image frame with a corresponding background value of the background pixel to determine whether the background pixel is related to the moving object.