Air-assisted steam stimulation (huff and puff) is an innovative process for enhanced heavy oil recovery. In this paper, the low-temperature oxidation (LTO) and coking experiments were conducted to reveal the LTO characteristics of heavy oils and its effect on the oil critical coking temperature. The O-2 consuming ability and oxidation activity of different oils, in a temperature range of 80170 degrees C, were analyzed, including typical light and heavy oil samples. The experimental results show that heavy oils have a higher oxidation activity at low temperature than that of light oils. Heavy oils can effectively consume O-2 in the injected air and produce a certain amount of CO2 under reservoir conditions. In terms of the difference in LTO characteristics of different oils, a more general LTO reaction kinetics model of crude oils in a reservoir was established. A parameter, Rdec (ratio of hydrocarbon oxides participating in decarbonylation to total hydrocarbon oxides produced from oxidation), is introduced to indicate the O2CO2 conversion features of different oils during the LTO process. The Rdec, Ea, and ko of heavy oils are usually lower than those of light oils, which can well reflect the LTO characteristics of heavy oils and demonstrate that heavy oils are more easily oxidized at a low temperature. However, because of more heavy oil components generated during the LTO process, the critical coking temperature of heavy oils exposed to an air environment will decrease (by 120 degrees C from 400 to 280 degrees C for super heavy oil). It should be noted that the effect of the LTO process on the critical coking temperature is different for different heavy oils, and the induced coking risks are also different in different heavy oil reservoirs, which need further studies in the laboratory and field.