Amix control driving method of passive matrix OLED(PM2OLED) is described to drive high gray scale display. The method is based on mix control of current digital to analog converter(DAC) and digital space time modulation (DSTM). The low bit gray scale is driven by the DAC while the high bitgray scale is generated by DSTM. This method is applied to a 128×128 dots RGB PM2OLED panel which can drive 512 gray scales.