The Yingqiong basin possesses abundant natural gas resources; nevertheless, except for a few large gas fields which have already been put into production, the exploration extent there is rather low. As the drill holes are insufficient in this basin it's very difficult to understand the longitudinal and horizontal variation trends of the velocity. Besides, the work of velocity calibration often encounters remarkable errors, which causes difficulty in drill hole employment. There exist mainly two difficult problems: one is the existence of considerable error between the predicted depth and the drilling depth when the time-depth relationship of the surrounding drilled well is adopted; the other is the existence of rather large deviation between the VSP calibration velocity of DFIPO well in Dongfang diapiric area of the Yingqiong basin and the regional velocity. Aimed at solving these two difficult problems, the authors conducted methodological study and put forward effective train of thought and means, thus improving the accuracy of velocity prediction in the study area.