In this paper, in order to enhance the performance of fabricated ZnO nanowires (NWs) by chemical vapor deposition (CVD) without catalysts, oxygen plasma was used to modify the ZnO nanowire-based interdigital microelectrode array photodetectors (IDA-PDs) at different times. The surface states of ZnO NWs with O-2 plasma treatment were characterized via X-ray photoelectron spectroscopy (XPS). Results showed that the photocurrent of the IDA-PDs continuously increased from 4 to 28 A as the plasma-treatment time increased from 0 to 10 minutes. The response mechanism of O-2 plasma treated ZnO NWs was investigated by illustrating the intensity of the surface oxygen atoms of ZnO NWs.This sample handling method can be beneficial in improving the performance of semiconductor photodetectors.