Abstract: The multi-rate variable well testing can weaken wellbore storage, shorten test time and economize the cost of test, and the contradiction between test and production is also solved to some degree. However, the corresponding interpretation method can only interpret the build up test data. In the paper a kind of pressure function (variable rate superposition equivalent time function) is introduced according to the superposition theory. The method adapts to the interpretation of the draw down and build up data. The oneness of the method between the superposition time function of variable flow rate is testified. At last the paper takes practical data for example.