Abstract: As the well pattern of Sazhong block in Daqing oilfield is dense, in order to gurantee new wells trajectory, avoid old wells and make wellbore trajectory accurately into the target layer, the cylindrical target directional well with small radius should be required. Through optimization of profile design and bottom hole assembly (BHA), the effect regularity on wellbore trajectory has been summarized and a set of drilling technology for cylindrical target directional well with small radius has been established. The application results indicate good drilling effects have been achieved.