Disclosed herein are an OLED display panel further including a switching transistor for controlling application of supply voltage in the initializing interval of a pixel, an OLED display device including the same, and a method for driving the same. The OLED display panel avoids a short-circuit between supply voltage VDD_EL and reference voltage Vref to thereby reduce initialization voltage applied to the gate terminal of the driving transistor T_dr. The OLED display device can achieve various effects such as improved response characteristics of pixels by reducing deviation in the initial voltage used in sampling.