The present disclosure discloses a pixel unit circuit and an OLED display apparatus. The pixel unit circuit comprises a first sub-circuit module, a second sub-circuit module, a first capacitor and OLED. An input of the first sub-circuit module is connected to a data line; another input of the first sub-circuit module is connected to an output of the second sub-circuit module and a first terminal of the OLED; an output of the first sub-circuit module is connected to an input/output of the second sub-circuit module via the first capacitor; a voltage difference between positive power supply and negative power supply of a backboard is applied between an input of the second sub-circuit module and a second terminal of the OLED. The pixel unit circuit can compensate the aging of OLED devices, the non-uniformity of threshold voltage of TFT driving transistors, and IR Drop of the power supply of the backboard.