Abstract: Based on the feature of in?situ combustion, the characteristics of temperature, pressure, fluid and reservoir rocks in heavy oil reservoir after steam huff and puff as well as their influences on the subsequent in?situ combustion are analyzed, focusing on discussion of the screening of appropriate in?situ combustion reservoir, decision?making and control of in?situ combustion process, reservoir screening function and horizontal well in?situ combustion performance. Through relationship between water saturation and front temperature of in?situ combustion given by principle of energy conservation, it is suggested that there is no need to convert wet combustion in advance from steam huff and puff followed by in?situ combustion. And combining with in?situ combustion test data, the impact of the complicated steam?breakthrough channels caused by steam huff and puff on the advancing of in?situ combustion front and the control factors are discussed. The studies show it is feasible to convert in?situ combustion from steam huff and puff