By using organic semiconductor CuPc as photosensitive materials, we prepared an organic thin film transistor with the vertical structure consisted of metal Cu/ organic semiconductor CuPc/ Al/ organic semiconductor CuPc/ indium tin oxide ITO. CuPc semiconductor material has good photosensitive properties in the 700 nm light. When the light signal irradiates organic semiconductor photosensitive material, the electron-hole exciton is separated into photocurrent in built-in electric field produced by organic semiconductor material/ metal schottky contact. It transforms into the driving current of organic photoelectric triode. By using its current amplification effect, the output current increase obviously. The test result shows that the I-V characteristics of the transistor are obvious unsaturated triode characteristics. When using 700 nm light to irradiate the device, the working current of the device increases obviously.