As an effective enhanced oil recovery (EOR) method in the late stage of the steam injection process, in situ combustion (ISC) has been verified by more and more researchers owing to its high recovery efficiency and low operation cost. However, the ISC process is prone to bringing about an unfavorable result with a low sweep efficiency and even an extinction process due to the complexity and uncertainty in oil and water distribution as well as the heterogeneity of the actual reservoir. In this work, combustion tube experiments combined with numerical simulations by CMG-STARS were conducted to study the influence of a reservoir′s physical parameters on the stability of ISC. It was found that the sustainability of the combustion process is sensitive to permeability and oil saturation, the lower limits of which are determined as 0.2 μm2 and 0.2, respectively. Then, a formula was preliminarily proposed as 0.25 ≤ So/K ≤ 0.8, which could be used as a reference of screening criteria in designing the ISC process.