C60 films fabricated by high vacuum deposition technique are studied by time-resolved photoluminescence spectrscopy from 127 K to room temperature. At 127 K, the peak of the C60 PL emission is at 730 nm and its decay behaviour shows single-exponential character. With the increase of the temperature, the PL peak has a red-shift and its decay obviously deviates from the single-exponential character. Adapting a four-energy-level model, we have got double-exponential decay solution for PL emission and then used this solution to fit the experimental data. The results demonstrate that the intersystem crossing rate of the singlet excited states increases rapidly with the increase of the temperature.