The invention discloses a pixel circuit as well as a driving method, a display panel and a display device thereof. The pixel circuit comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a driving transistor, a first capacitor, a second capacitor and a light-emitting element, through the cooperating driving between all transistors and the two capacitors, the driving current is enabled to be unrelated to the threshold voltage of the driving transistor and the step voltage of the two ends of the light-emitting element finally. According to the pixel circuit as well as the driving method, the display panel and the display device thereof, the influence of undesirable factors is eliminated, the problem that the conventional display device is uneven in light emission is further improved effectively, and the uniformity of luminance and the display effect of the display device are improved.