During the procedure of in situ combustion (ISC) for heavy oil, the rate of heat release at the low temperature oxidation (LTO) stage directly affects the delay time and the effect of ignition. This paper aimed at various clay minerals effects on heavy oil oxidation before ignition, at different reservoir temperatures and air/oil ratios, using a small batch reactor (SBR). Characterizations of the pressure, the reaction temperature, the post-test gases, the viscosity, and the asphalt content of heavy oil before and after oxidation were carried out. The results indicated that the catalysis of clay minerals was enhanced with the increase of temperature and air/oil ratio. At a rather lower temperature (90 degrees C), all three types of clay minerals did not obviously affect the temperature increment or rising rate at LTO while they had a little effect on viscosity, but had great influence on asphalt content, which increased greatly after the reaction. At a rather higher temperature (150 degrees C), clay minerals had great influence on the heat release. Montmorillonite had the best catalytic effect, which was 4.28 times higher than the blank sample in temperature rising rate under a higher air/oil condition, while the viscosity of crude oil reduced, and the concentration of asphalt slightly increased after reaction. The results of this study provide new insight that the clay minerals in the reservoir or injecting a certain amount of clay minerals into the reservoir before ignition can accelerate the reaction rate and heat release rate, thus improving the ignition effect.