The effects of the oil acid number, alkaline concentration and type, brine salinity, and test temperature on alkaline flooding for heavy oil are investigated in this study. The results indicate that the tertiary oil recovery is positively affected by the oil acid number, which is a prominent factor in alkaline flooding. Another important factor is alkaline fluid. The best displacement efficiency can be achieved only when the alkaline concentration reaches a certain value. However, honeycomb oil blocks with a poor mobility may form when the alkaline concentration is too high. In comparison to Na2CO3, NaOH performs better in alkaline flooding for Zhuangxi 106 heavy oil. In addition, the performance of alkaline flooding is also affected by the brine salinity and test temperature. There is an optimum brine salinity for alkaline flooding, and the relatively low temperature is beneficial to alkaline flooding. When the temperature increases to a certain value, the displacement efficiency declines intensively. All of these results can be explained on the basis of the special flow mechanism of alkaline solution in the heavy-oil phase during flooding.