Photo-thermal effect is one of the most important effects in the interactions between laser and biological tissue cells, however, its generation, transmission and action mechanisms are not yet clear. When laser irradiates biological cells, temperature is the decisive parameter in that temperature change in biological cells reflects a variety of physical properties of cells, which plays an important role in clinical applications. A numerical simulation model is built, and the heat accumulation process is simulated and analyzed using finite element software according to the heat transfer equations when laser irradiates biological cells. The temperature variation process of biological cells under different chopping cycles is analyzed, and equations of two temperature rise processes and two temperature drop processes are fitted when the chopper period is 0.1 s and the irradiation time is 0.2 s. It is concluded that the phenomenon of heat accumulation will appear only when the chopping frequency reaches a certain value; the highest temperature of thermal model which is irradiated by laser is related to the chopping frequency, and the higher the chopping frequency is, the lower the biological cell′s thermal effect is.