A correction method of a cathode voltage is provided, including: controlling an image generator to send a first image test signal including a cathode voltage to a display module to be tested at each brightness level of the display module to be tested; controlling an optical measuring device to measure a first display parameter of the image displayed by the display module to be tested according to the first image test signal; obtaining the first display parameter from the optical measuring device, and determining whether the first display parameter is within a display parameter threshold ramie; progressively adjusting the cathode voltage according to a determination result, and using a second image test signal including an adjusted cathode voltage to test the display module to be tested and obtain a second display parameter until a corrected cathode voltage at a current brightness level is obtained.