High performance ultraviolet(UV) photodetectors(PDs) are critical for the high-speed optical communication and environmental sensing. Here, the performance of ZnO PDs was improved by directly fabricating photoelectric device on the ZnO nanowires(NWs) networks made by chemical vapor deposition (CVD) without any seed layer or metal catalyst. Results showed that the photocurrent of the ZnO NWs networks PDs is 60 ?滋A, which was about 15 times of the single ZnO NW PDs. The response mechanism of ZnO NWs networks PDs was investigated in detail. Specially, the interconnections in ZnO NWs networks creat NW-NW junction barriers, which dominate the inter-wire charge transport. The fast tuning of NWs networks junction barrier height under the UV radiation, which contributes to the enhanced performance of the ZnO NWs networks UV PDs.