The invention provides a pixel driving circuit and method for an organic light emitting diode. The pixel driving circuit comprises a first transistor (T1), a second transistor (T2), a third transistor (T3), a fourth transistor (T4), a fifth transistor (T5), a sixth transistor (T6), a storage capacitor (C1) and the organic light emitting diode (OLED), and further comprises a scanning control end (Scan), a data signal end (Data), a constant flow source (Iref), a control light emitting signal end (Em), a power supply voltage (VDD) and a power supply negative electrode (VSS). The first transistor (T1) is a driving transistor. According to the pixel driving circuit and method for the organic light emitting diode, a 6T1C compensating circuit is adopted for carrying out compensation on a threshold voltage (Vth) of the driving transistor in each pixel, the threshold voltage (Vth) is captured through the constant flow source (Iref), data writing in and threshold voltage (Vth) capturing are carried out at the same time, the changes of the threshold voltage (Vth) of the driving transistor are effectively compensated for, and the display quality is improved.