In order to speed up the development of tight oil and improve the horizontal well drilling technology of tight reservoir in Yanchang oilfield，meanwhile，aiming at the polyacrylamide potassium salt（K-PAM）polymer drilling fluid system used in the current stage of Yanchang oilfield had shortcomings such as poor rheology，insufficient plugging and inhibition，the indoor optimization of the commonly used fluid loss reducer，inhibitor，lubricant，plugging agent and other treatment agent was preferred to obtain a formula of strong plugging type nano-polymeric alcohol water-based drilling fluid suitable for tight reservoir. Finally，the drilling fluid was applied in the field. The results showed that the polymer fluid loss additive COP-FL could significantly improve the water loss and wall-forming property of the system. The non-fluorescent anti-collapse lubricant FT342 had strong inhibition. The liquid extreme pressure lubricant JM-1 had good overall lubrication effect. And blocking agent anhydrous polymeric alcohol WJH-1 and nano-emulsion RL-2 could increase the drilling fluid blocking rate by 51.7%，which could enhance the wellbore stability. The horizontal section strong plugging type drilling fluid system，whose formula was 4% sodium bentonite，0.2% soda ash，0.4% K-PAM，2% COP-FL，1.5% FT342，1.0% JM-1，5% WJH-1 and 3% RL-2，was applied to two horizontal wells in tight reservoir of Yanchang oilfield. During the construction process，the system had good leakage prevention and sealing effect. The mechanical drilling speed increased by 30% compared with the adjacent one，the construction period shortened by 35% ，the downhole accident rate reduced by 85.7%，and the drilling cost reduced by 34.7%，which provided effective technical support for the excellent drilling of horizontal wells in tight reservoir of Yanchang oilfield.