As a novel and effective approach, response surface model is used in the study of drug-drug interactions. When two drugs are used simultaneously, this model can be applied to estimate the key characters of the response surface, to find the desired response region by optimal drugs combination, to explore the mechanism of drug-drug interactions, and thus to guide sound clinical application and reduce the risk and cost. In this article, the model's basic mathematical and pharmacological concepts are introduced, and its research progresses are reviewed.