Abstract: Due to the poor lubricity and high friction during the drilling of horizontal wells by using high-density water-based drilling fluids, the lubrication and friction reduction technology was studied, and factors influencing the lubricity and friction reduction performance of high-density drilling fluids were analyzed. Subsequently, lubricant Rhj-1, a lubricant with long-chain fatty acid vegetable oil as the raw material, was developed. The performance evaluation results showed that the lubricant RHJ-1 could reduce the extreme pressure lubrication coefficient of 5.0% bentonite slurry to 0.040. The lubrication coefficient of drilling fluid with a density of 2.10 kg/L could be reduced to a minimum of 0.105 after adding lubricant RHJ-1, and its temperature resistance ability could reach 150 ℃. For the drilling fluids with cuttings powder dosages of 10.0% and 15.0%, when the dosage of lubricant RHJ-1 was increased to 4.0%, the maximum reduction rate of drilling fluid lubrication coefficient could reach 55.58%. In order to ensure the lubricity and friction reduction of high-density drilling fluids in drilling horizontal wells, technical measures such as controlling the solid content and making use of the "bearing" effect of weighting agent, etc. were taken, thereby forming the lubrication and friction reduction technology for high-density drilling fluids. This technology was tested in Well WY23-4HF located in the deep shale gas block in Southwest China, and the tripping out friction after drilling was only 300 kN, which fully met the requirements of lubrication and friction reduction in the drilling of horizontal section. The results showed that the high-density drilling fluid technology for lubrication and friction reduction for horizontal wells is feasible and effective, and is worthy for popularization and application.