A complementary thin film transistor driving back plate and a preparing method thereof, and a display device are disclosed. The preparing method comprises: forming a lower electrode (102) on a base substrate (101); sequentially disposing a continuously grown dielectric layer (103), a semiconductor layer (104), and a diffusion protection layer (105); sequentially forming a no-photoresist region (107), an N-type thin film transistor preparation region (108), and a P-type thin film transistor preparation region (109); removing a photoresist layer (114) of the N-type thin film transistor preparation region (108); removing a diffusion protection layer (105) of the N-type thin film transistor preparation region (105); removing a photoresist layer (114) of the P-type thin film transistor preparation region (109); performing an oxidation treatment to the base substrate (101); disposing a passivation layer (111) on the base substrate (101); and forming an upper electrode (113) on the passivation layer (111).