OBJECTIVE To observe Staphylococcus aureus(SAU) infection at high altitude and plain after gunshot injury. METHODS Used 7.62mm bullets to injure posterior limbs of piglets with the same age.We got contusing tissues in different time after injury,to make bacteriologic examination,identify and make a statistic analysis of SAU. RESULTS The main infection was caused by SAU after gunshot injury in two regions.From contusing tissues in two regions,the rate of contamination caused by SAU in Chongqing and Lasa was 48% and 18%,respectively.The time of SAU colonization was 3 hours at high altitude,and less 3 hours at plain.The velocity of reproduction of SAU at high altitude for 12 hours was 5-6 passages,and at plain was 4-6 passages for 3-6h.The time of remaining relative steady state between tissues and germs was 48 hours at high aititude and 24 hours at plain.The difference of the number of SAU between two regions after injury 3-36 hours was significant,But after 36 hours the difference was unsignificant. CONCLUSIONS At high altitude region,SAU is the main germ that causes contamination after gunshot injury,the velocity of reproduction of SAU is slower than that at plain,the time of infection is delayed obviously.