With some heavy oil blocks of Bohai oilfield having been in the afternoon of development life, encryption adjustment of horizontal well will become more important to increase and stabilize oil production. But this kind well has very big risks of penetration crossing, complex trajectory and high downhole friction. Usually advanced foreign rotary steering tools are used in offshore oilfield for its safety and time efficiency with high cost, which is difficult to popularize. By a series of researches on trajectory control technologies in Bohai oilfield, the complete well drilling by conventional mud motor has been realized. The paper summed up the trajectory control technology for encryption adjustment well with a difficult S-type encryption adjustment horizontal well to provide some experiences for the similar wells.