Poor drilling efficiency in deep formation and serious bit wearing are caused by gravel-containing formation, hard rock and roller cone drilling for more than 85% of the well sections in Gucheng region of Tadong block of Daching. Based on the traditional drilling speed prediction method, the calculation method of rock breaking efficiency is established by introducing the related parameters of bit wearing, formation lithology, well depth and so on, and based on the formation lithology, logging data and drill bit types, the optimization model of drill bit is set up to realize quantitative bit selection, bit series recommendations suitable for Gucheng region is put forward, which was successfully applied in 5 wells, the footage of single bit and the average penetration rate have been greatly improved, the bit optimization provides technical basis for efficient drilling construction in Gucheng region.