Prostate protein antigen (PSA) was detected sensitively on a split electrode array equipped with a photoelectrochemical microdevice.In the study,we combined the photoelectrochemical electrode and detection electrodes (split electrode) on a chip.A 1st antibody of PSA was inmmobilized on split elecodes and PSA was captured on it by immunological reaction.Ater that,the 2nd antibody of PSA labelled by Au nanoparticle was held by the PSA.A silver enhancement solution was covered on the antingen-antibody complex and Ag was deposited on Au nanoparticles after minutes.Finally photocurrent come from the photoelectrode flowed through Ag deposit and the amount of PSA was detected.