In order to study the ZnO photoresponse mechanism, a platform that can perform the photocurrent spectrum measurement has been designed. By using our platform, the photocurrent spectrum of porous ZnO film sensitized by metal chloride solutions was obtained. We used the screen printing technique to fabricate the material chip. The measurements were performed in dry air (relative humidity 15%) and at room temperature. We observed two peaks in the photocurrent spectrum. The peak at 380nm is assigned to the exciton transition. The shoulder peak at 480nm is owed to surface states introduced by sensitization and we find V-Zn plays an important role on this phenomenon. A model is proposed to explain the phenomenon. Furthermore, it is suggested that our platform is a useful tool for photoresponse research and can offer an effective guidance for further investment of light activated gas sensors. (C) 2012 Elsevier B. V. All rights reserved.