Abstract: With pressure data of the pressure profile acquired with the modular formation dynamics tester tool (MDT), the oil, gas and water zones/layers can be identified in general. But there exists erroneous adjustment probability of reservoir fluid property, due to various influencing factors in the process of well testing. With the method of well test analysis, this paper determines whether the MDT measures the real formation pressure or not, and proposes the choice of accepting the data or rejecting them given by MDT. The field application indicates that this method can be used to get good results in field application