In the horizontal well drilling construction in Mo116 well area, which is located in the south of Mobei oilfield, there are the challenges of undergauge, drilling tool jamming, borehole collapse, mud loss, blowout and hard rocks. The optimization of horizontal well design and technical study on drilling trajectory control are carried out in this area to avoid complex downhole accidents, shorten drilling cycle and reduce operating risk. According to the analysis on drilling data of this area, the optimization schemes of wellbore structure and well trajectory control are put forward; based on the analysis on previous drilling data and drill string mechanics, the horizontal drilling BHA and drilling parameters are optimized; through the drilling fluid system optimization, the poor borehole wall stability, high friction and sticking probability in directional drilling sections are improved. By the application results, optimal and fast drilling in horizontal wells is realized, the average ROP of the second directional interval and the third interval are increased by 27% and 30% respectively than those before optimization, and one trip is realized in M614 and other wells for horizontal sections drilling.