Abstract: In order to safely and efficiently drill the long lateral horizontal wells in the tight reservoirs of the Cangdong Sag, a team analyzed the characteristics of the strata as well as the drilling challenges such as large friction torque, well trajectory control difficulty, low ROP in the purple-red mudstone, and drilling fluid contamination in gypsum layer. The key technologies and guidelines for horizontal well drilling in the tight reservoirs of Cangdong Sag were formed by developing casing program optimization, well trajectory and its control design, drilling equipment and tools optimization, drilling fluid system optimization, rapid and efficient drilling technical measures optimization and safety casing RIH methods selection,. Field tests on two wells of GD1701H and GD1702H show that the application of key drilling technologies can successfully overcome such drilling challenges as difficulty in controlling the well trajectory, stringent requirements for drilling fluid anti-gypsum contamination and lubrication/anti-sticking, and low ROP in Kongdian Group. According to the comprehensive research, the key technologies of horizontal well drilling in tight oil and gas reservoirs of Cangdong Sag have achieved good results in field applications, which can provide technical support in horizontal well drilling for similar reservoirs, and can be promoted widely.