Due to long horizontal displacement，large deviation angle，high formation pressure coefficient and high friction torque during completion，the running of string is affected. In order to solve this problem，a kind of completion fluid lubricant CR301 was developed in laboratory，and the friction reducing and drag reducing performance，anti-friction ability，compatibility，reservoir protection effect and water locking effect of KCl brine completion fluid system with the lubricant were studied. The results showed that when the dosage of CR301 was 2%，the friction coefficient of KCl brine completion fluid decreased from 0.078 to 0.046，the friction coefficient decreased by more than 40%，and the anti-friction ability increased from 4 weights to 10 weights. At the same time，CR301 had good compatibility with KCl brine completion fluid，which could improve the permeability recovery value of core，reduce the surface tension of completion fluid system and reduce reservoir damage. CR301 could obviously improve the drag reduction performance of KCl brine completion fluid system，and had protective effect on reservoir，so it could be used in extended reach well completion fluid.