A test system for testing an image processor of an electronic device by controlling the image processor to playback a test image divided into several pixel areas is provided, therein, each pixel area includes several rows of pixels, and pixel values of the rows of pixels of one pixel area are respectively the same. The test system includes a storage device, a test module, and a test device. The storage device stores a pixel value of one row of each pixel area, and position of the pixel areas of the test image (test data). When the electronic device connects to the storage device, the test module invokes the test data from the storage device, recovers the test image according to the test data, and controls the image processor to produce a corresponding image signal. The test device judges performance of the image processor according to the image signal.