The ZnO/n+-Si heterojunction has been fabricated via depositing nominally undoped ZnO film by reactive sputtering on a heavily arsenic-doped (n+) silicon substrate. The sputtered ZnO film was n-type in conductivity with an electron concentration of 1.0×1018 cm-3. The current-voltage characteristics indicate that the ZnO/n+-Si heterojunction does not possess rectifying function. Under the forward bias with the negative voltage applied on the n+-Si substrate, the heterojunction emits ultraviolet and broad visible lights characteristics of near-band-edge and defect-related emissions of ZnO, respectively. The EL mechanism has been tentatively explained in terms of the energy-band diagram.