A display device testing system and a method for testing a display device using the same, which are capable of testing whether a display panel is defective or not according to a variation of the frame frequency and whether the driver module operates normally or not even at a voltage higher than a normal operation voltage. The display device testing system includes a display panel including a plurality of gate lines; a driver module including a gate driver unit for sequentially supplying a gate voltage to the plurality of gate lines in response to a test, vertical synchronization start signal; and a testing module for supplying a test vertical synchronization start signal to the driver module.