To obtain better laser exposal parameters in the laser medicine clinic, a finite-element method was adopted to simulate the human skin's opto-thermal response when irradiated by pulsed laser and continuons-wave (CW) laser. The differences of tissue temperature caused by pulsed laser and CW laser were compared. The relationships between thermal response time, thermal relaxation time and depth of skin were achieved. With increasing the skin's depth (0～60 μm), the thermal response time (0～4 ms) and relaxation time (0.4～12.1 ms) became longer. The temperature rise of tissue induced by different pulse width was studied. An evaluation function δ was established to evaluate the loss of heat. Based on δ, the selection of pulse interval was analyzed.