An organic light emitting diode (OLED) display and a driving method thereof include an OLED, a driving transistor supplying a driving current to the OLED, a data line transmitting a data signal to the driving transistor, a first switch including a first electrode connected to one electrode of the OLED and a second electrode connected to the data line, and a second switch including a first electrode connected to the data line and a second electrode connected to the gate electrode of the driving transistor. The first switch is turned on such that a predetermined first current is transmitted to the OLED, the voltage of one electrode of the OLED is received through the data line, the deterioration degree of the OLED is detected according to the transmitted voltage, and the data signal transmitted to the data line is compensated according to the detected deterioration.