The In-situ coring has a significant effect on the exploration of deep earth. However, in deep hard rock coring, the cutting heat in the process of coring generates high temperature and causes fidelity distortion of the in-situ core. Exploration of the mechanism of heat effect in the coring process is necessary to achieve the continuous control of temperature and obtain in-situ core. Due to the lack of systematic study on the surface and internal temperature rise of core samples during coring process, this paper uses the finite element simulation study the heat effect on the surface of the core under the influence of various cutting parameters. The numerical simulation results show that the surface of the core will not be burned under the cutting speed of 100 mm/s. At the condition of cutting speed 100 mm/s, feed rate 0.03 mm/r, thermal conductivity coefficient 1 W/m°C, the whole temperature rise will not exceed 1°C. The interest results showed that cutting fluid has little effect on the temperature rise in the cutting process. If the requirement of core quality should avoid the pollution by drilling fluid, this study has supported the no drilling fluid for in-situ coring.