In this work, the TiO2/Sb2S3 nanorod arrays (NRAs) were synthesized through a two-stage hydrothermal route for photoelectrochemical (PEC) water splitting. The effect of annealing treatment in Ar ambience on the PEC activity of TiO2/Sb2S3 composite sample was investigated by electrochemical impedance analysis, including Nyquist and Mott-Schottky (M-S) plots. It was demonstrated that vacuum annealing could crystallize Sb2S3 component and change its color from red to black, leading to an increment of photocurrent density from 1.9 A/m2 to 4.25 A/m2 at 0 V versus saturated calomel electrode (VSCE). The enhanced PEC performance was mainly attributed to the improved visible light absorption. Moreover, annealing treatment facilitated retarding the electron-hole recombination occurred at the solid/liquid interfaces. Our work might provide a novel strategy for enhancing the PEC performance of a semiconductor electrode.