In the process of managed pressure drilling,the conventional drilling throttle valve has a large pressure drop gradient and strong erosion,and the error is large when the switching degree control precision is 3% ~ 5%,which can not meet the requirements of fine pressure control technology.To solve the above problems,the mechanical model of PFF series straight-through flat plate throttle valve was established by using CAD and fluid simulation software,and the change of spool pressure drop under different opening degrees was analyzed.The simulation results were consistent with the actual recorded results.After optimization scheme based on shunt decompression,a new shield typethrottle valve hole was designed.The optimization results show that the pressure drop of the new straight-through flat plate throttle valve in the commonly opening range (20% ~ 40%) is linear changed,the pressure drop correlation can reach more than 88%,the optimized scheme greatly extends the life of the throttle valve.