We measured the absorption and photoluminescence spectra of the organic semiconductor CuPc(Copper Phthalocyanine)under various temperatures to discuss that how temperature affects the situation of electrons transition and efficient of CuPc in organic thin film solar cells. The experiment result reveals that absorption spectra without peak shift and intensity change when increasing the temperature. Photoluminescence spectra also without peak shift but intensity increases with decreasing temperature. Simultaneously , the photoluminescence with a phonon involved is more obvious. From this observation, we conclude that the working efficient of CuPc in solar cells may decrease with decreasing temperature.