By the thin film model and the local thermal equilibrium assumption, the instantaneous radiation power and instantaneous radiation energy flux near the event horizon of the dynamic spherically symmetric black hole have been studied. When the cut-off distance η takes a fixed value, the following results can be obtained. For Vaidya black hole, its instantaneous radiation energy flux of the scalar field near the event horizon is related to both the black hole mass and the change rate of the event horizon. But its instantaneous radiation power is only related to the change rate of the horizon. For Vaidya-Bonner black hole, the instantaneous radiation power and instantaneous radiation energy flux are all related to the mass, the charge of the black hole and the change rate of the event horizon. These results show that the gravitational field, electromagnetic field and the change of the horizon will all affect the thermal radiation of the black hole.