Friction wear and sealing performance are important indexes to evaluate the valve stem packing sealing system.Based on a new comprehensive test system for the friction characteristics and sealing performance of packing modified by control valve,the influence of the cross section shape and combination of graphite packing on the friction characteristics,wear characteristics and sealing performance of packing was investigated by dynamically monitoring the mechanical changes of valve stem and the leakage rate of packing box.The experimental results show that the level of dynamic friction of the graphite packing with different cross section shapes is lower than that of the graphite packing with different combination modes under the same conditions,and the friction of the valve closed downward is greater than that of the valve opened.With the increase of the number of cycles,the starting friction of the sample decreases,the sliding friction increases slightly,the wear of the packing deteriorates,and the leakage rate increases.For the three sections of cone shaped,V-shaped and diamond shaped,V-shaped section has the smallest starting friction,the lowest requirements for actuator configuration,diamond shaped section has the smallest sliding friction,the lowest influence on the position accuracy of the control valve.For the two combination modes of two-sided type and alternating type,the alternating type combination reduces the packing friction by 35% by adjusting the radial stress distribution,the sealing characteristics and comprehensive performance of graphite packing are significantly improved.