A constant current electrodeposition approach was employed to prepare Cu2O/TiO2 nanocomposite thin film. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman, ultraviolet visible light spectrophotometer (UV-Vis), and photoluminescence (PL) measurements were used to characterize and analyze the thin film microstructure, surface morphology, and photoelectric properties. The effect of annealing treatment on the thin film properties is discussed. The response surface methodology (RSM) was employed to optimize the Rhodamine B (RhB) photocatalytic degradation by thin films, and the quadratic multinomial mathematical model was established. The photocatalytic degradation process of RhB was also studied. The results indicate that the prepared Cu2O thin film was of high purity, with a (111) crystal plane preferred orientation. The average particle diameter was approximately 100-200 nm, and the absorbing boundary was approximately 600 nm. After annealing treatment, the absorbing boundary and open-circuit voltage increased, and Cu2O thin film exhibited an obvious absorbance response in the visible-light range. The established model has better fitness and higher reliability, and the R2 value of established quadratic model is 0.9818. The optimal degradation conditions were obtained by RSM. Under optimum conditions, the RhB degradation rate could reach 98.4% in 3 h and the total organic carbon (TOC) removal rate was 48.2%. Recycling results reveal that RhB degradation rate can still reach 94.5% after eight cycles.