Provided is a compensation method of a cathode voltage drop of an OLED display device and a pixel driving circuit. The first pixel driving circuits having function of detecting the cathode voltage are arranged in a portion of sub pixels of the OLED display device and uses the first pixel driving circuits to detect the cathode voltages of these sub pixels. The cathode voltages inputted to all the sub pixels of the OLED display device are obtained by interpolation according to the detected cathode voltages of these detecting sub pixels. Then, the cathode voltage compensation look up table is obtained according to the cathode voltages of all the sub pixels of the OLED display device. Finally, the data signal voltage is compensated with the cathode voltage compensation look up table. The data signal voltage after compensation is used to drive the OLED display device to perform image display.