ObjectiveTo evaluate antimicrobial resistance of bacteria in nosocomial infection (NI) and changing trend.MethodsAntimicrobial resistant results of bacteria reported to China  Nosocomial Infection Surveillance System (CNISS) by national wide hospitals between January, 1999 and December 2007 were analyzed statistically.ResultsAmong grampositive bacteria, Staphylococcus and Enterococcus were the most sensitive bacteria to vancomycin, sensitive rate was more than 96%; the detection rate of methicillinresistant Staphylococcus aureus, methicillinresistant Staphylococcus epidermidis, methicillinresistant Staphylococcus haemolyticus，penicillinresistant Streptococcus pneumoniae was 80.18%, 77.19%,  90.71%  and 43.84% respectively; the resistant rate of Enterococcus faecalis and Enterococcus faecium to ampicillin was 30.15% and 81.60% respectively. Among gramnegative bacilli, the common bacteria in Enterobacteriaceae were most sensitive to meropenem, which was more than 89%, the next was imipenem(88%); the resistant rates of nonfermentative bacteria including Pseudomonas spp., Acinetobacter spp., and Stenotrophomonas spp. to cefoperazone/sulbactam was the lowest, which was 28.86%,18.53% and 20.85% respectively, the resistant rate of Pseudomonas spp. and Acinetobacter spp. to imipenem was 33.81% and 22.86% respectively. Compared with resistant rate to piperacillin and cefoperazone, the resistant rate of common gramnegative bacteria  to piperacillin/tazobactam and cefoperazone/sulbactam decreased markedly (P<0.05). Comparison among drugresistant rates  from January, 2005-December, 2007 and January,1999-December, 2001 showed that drugresistant rates of bacteria increased 30% were as follows: Staphylococcus epidermidis to imipenem, Enterococcus faecalis to piperacillin, Enterococcus faecium to penicillin and amoxicillin/clavulanate, Escherichia coli to cefepime, Pseudomonas aeruginosa to ticarcillin/clavulanate, Acinetobacter baumannii to ampicillin/sulbactam, amoxicillin/clavulanate and imipenem, Stenotrophmonas maltophilia to ampicillin/sulbactam. Drugresistance increased most rapidly was Acinetobacter baumannii, and resistance to the third generation cephalosporins increased most rapidly.ConclusionDrugresistant rate in NI is high, and most are multiple drugresistance; antimicrobial agents with enzymeinhibitors are more sensitive than non enzymeinhibitors; the resistance has  tendency of increasing, especially Acinetobacter baumannii and the third generation cephalosporins.