We studied the transient photoconductivity(PC) properties of GaN thin film on (0001) sapphire substrate. The decay curves of PC obtained by YAG:Nd pulsed laser are divided into two special regions, which are the beginning and tail decay regions, corresponding to two time constants, 0.1 ms and 1.0 ms, respectively. Keeping the same light intensity and bias voltage, when the sample was heated to 300°C, the time constants are both reduced. It shows that there are a large number of traps at the position of tens of meV above the valence band edge. The PC ascends S-shaped when the data were collected during the first 200 ns. As the sample is not shined, the PC sharply reduces and oscillates, indicating that the carriers redistributed between the deep traps and the valence band. The experiment results are explained by the model that involves two hole trapping levels, the shallow trapping level and the deep trapping level. Moreover, the mechanism of the curves varied as the light intensities are also explained by the model.