Abstract: Handling information on formation being drilled is a critical step of optimized drilling.Such parameters of formation features negatively affecting bit penetration,as drillability can be obtained mainly in the drilling process.Penetration time logging is an important method to get this kind of information.Penetration time and normalized penetration time math model have been given in the paper.An equation of the bit dulling trend has also been developed using the concept of homogeneous equavalent formation,so parameters of formation features can be determined.Two kinds of formation interface effect are analysed.Logging curves of a non-homogeneous formation of the Zhongyuan Oil Field and block diagram for data processing are shown and microcomputer results are given.