Abstract: A rock mechanics parameter model was established by using the logging data and combing with rock mechanics characteristics and the lithology profile of the offset well.This model was used to interpret the mechanics characteristics of the rock in longitudinal profile.Bit selection,mainly focused on PDC bit for the front-hill formation was presented,taking reference of the bit using in the offset well.Based on the formation lithology characteristics,the PDC bit was optimized from such aspects as the composite block,blade geometry,cutter model,and cutter mechanics balance,etc.The modified bit was successfully used in the front-hill formation in Tarim.