Abstract: In order to solve the problem of high friction and backing pressure in the process of horizontal well drilling,and improve the efficiency of horizontal well drilling,the hydro-oscillator was developmented.Based on the theory of mechanical vibration,downhole equipment would transfer static friction into kinetic friction between the drilling tools and borehole wall when the axial vibration is at a certain frequency,and the kinetic friction is smaller than static one.Hydro-oscillator uses drilling fluid as the driving force to drive the creep of drilling tool along the axial direction.It has been tested in Well Wei 186-Ping 142 and drilled 501.00 m in 96 hours.Drag force reduced 20-40 kN less than the normal,sliding was 36.77 m,ROP improved by 54.9%,and complex drilling was 464.23 m,ROP improved by 23%.The field test showed that the hydro-oscillator could reduce friction and backing pressure so as to improve penetration rate and reduce drilling cycle.