The rational design of heterojunction structure as photoanode provides an effective route to improve the efficiency of photoelectrochemical (PEC) water splitting. Herein, we design and fabricate CdS nanoparticle/TiO2 nanorod array heterostructures through a facile hydrothermal process. With the assistance of a ZnO interlayer between CdS and TiO2 prepared by atomic layer deposition technique followed by microwave hydrothermal reaction, uniform Zn-doped CdS/TiO2 shell/core arrays are attained. Via tuning the ZnO thickness and CdS deposition time, the optimum Zn-doped CdS/TiO2 sample exhibits a superior PEC performance with a photocurrent of 3.38 mA cm(-2) at 1.23 V versus RHE, which is 6.0 and 1.4 times higher than pristine TiO2 and CdS/TiO2, respectively. Moreover, the corresponding onset potential of Zn-doped CdS/TiO2 is obviously shifted toward the negative potential direction by 450 and 130 mV, respectively. The performance enhancement is attributed to the improved electron-hole transport and separation ability, stronger light absorption and higher photoactivity.