The invention discloses a method for detecting component size based on matching pursuit (MP) wavelet filtering. The method comprises the steps of (1), calibrating a charge coupled device (CCD) camera; (2), acquiring a component image and performing MP wavelet filtering on an image; (3), performing differential operator edge detection on the image; (4) performing sub-pixel edge detection on an edge pixel; and (5) calculating the size of the component according to a sub-pixel coordinate to generate computer-aided design (CAD) graph. According to the method, the image of the component is subjected to the MP wavelet filtering, the filtered image is subjected to the sub-pixel edge detection, and the size of the component is calculated and extracted according to the sub-pixel coordinate, so that the detection accuracy can be correspondingly improved, and the detection speed is quickened. The invention discloses a detecting system based on the detecting method. The system comprises an image acquisition unit, an image processing unit and an image generating unit. Because the camera is combined with a personal computer (PC), image acquisition and image processing on components on the production line can be realized, so that the timeliness for detecting the components is guaranteed.