Abstract: During the drilling of shale oil horizontal wells in Cangdong Sag of Dagang Oilfield, technical challenges such as low rock breaking efficiency, difficult borehole trajectory control, large friction torque and difficulty in completion string RIH were encountered, which compromised the exploration and development benefits of shale oil. To solve the problem, technical research was conducted which included the following: aggressive hydraulic parameter design, special-shaped tooth PDC bit development, deep horizontal section efficient drilling, rotary steering borehole trajectory control, strong inhibition/sealing high-performance water-based drilling fluid, and rotary guide shoe + rotary casing RIH. Together, they form a set of key shale oil horizontal well drilling technologies in Dagang Oilfield. Those technologies were applied in 13 shale oil horizontal wells, the average ROP of 13.16 m/h, drilling/completion period of 50.62 d and the downhole downtime rate of less than 0.1% were successfully achieved. The combined parameters set new records in well drilling in the Dagang Oilfield. The research and field application suggest that those key technologies have provided technical supports for the efficient exploration and development of shale oil in the Cangdong Sag, and they are of importance guidance for the safe and efficient drilling of horizontal shale oil wells in China.