This study was performed to investigate the effect of low power laser irradiation on Substance P(SP) expression in the burned skin of the rats. Burns of about 3cm in diameter were created with $75^{cric}C$ water on the back of the rats, and the lesion of experimental group were irradiated on days 1, 2, 3 and 4 postwounding. Control leasions were not irradiated. After burns, low power laser irradiation was applied by using 1000Hz, 830nm GaAlAs(Gallium-aluminum-arsenide) semiconductor diode laser. The expression of evaluated Substance P(SP) immunohistochemistry on rabbit anti-SP The results of this study wereas follows 1. The Substance P was expressed in the lamina I and II of dorsal horn of spinal cord. In expression of SP, the lesion of control group made SP to more induce significantly than experimental leasions. 2. SP immunoreactivity in burned leasion of spinal cord were decreased markedly 4 days after burns, and decreased gradually from 1 day to 2 days in burns which is laser irradiation These data suggest that low power laser have a pain release effect in the burned skin of the rats.