Abstract: OBJECTIVE To quantitatively analyze the steam penetration performance of the pulsating vaccum pressure steam sterilization process, And to analyze the factors that affect the actual sterilization effect of the sterilizer, and find an evaluation method. METHOD The spiral type lumen sterilization Process Challenge Device（PCD） with 13 steam penetration difficulties in increasing order was added with the chemical indicators unloaded or sterilized with the instrument to observe the passage of the chemical indicator. RESULTS The maximum successfully penetrated PCD results of full load were averagely 6.94, which was better comparing to that of empty load 4.17, proving that the loading capacity had an effect on the performance of a steam sterilization process in the same machine program. For the sterilization procedure of the fully loaded equipment on the same day, the hihgest difficulty value fluctuated between PCD 4# and 9#, and the fluctuation of the actual sterilization efficiency of the same sterilizer was random. CONCLUSION Due to the small loading capacity effect of the pressure steam sterilizer, certain loading requirements should be made in each sterilization operation. The actual sterilization effect of the pressure steam sterilizer will continuously fluctuate due to the influence of vacuum pump performance, steam quality and other factors during continuous operation. Because of the volatility of the sterilization effect, it is significant to use effective batch monitoring. The actual sterilizaion effect of the sterilizer should be checked regularly to ensure the aseptic quality, and protect the safety of patients.