Abstract: OBJECTIVE To monitor the plasma concentration of tigecycline in critically ill patients and calculate the PK/PD compliance rate to provide a reference for using tigecycline more rationally in clinic. METHODS The 45 critically ill patients included were divided into high and low dose groups. The trough concentration, intermediate concentration, and peak concentration(C_min, C_1/2t, C_max) after the 7th administration were collected. Caculated the AUC_0-24 and AUIC values and PK/PD compliance rate at different infection sites, and observed 2 groups of adverse reaction conditions. RESULTS The C_min, C_1/2t, C_max, AUC_0-24, and the overall compliance rate of PK/PD in the high-dose group were significantly higher than those in the low-dose group(P<0.05). The compliance rate of high-dose group in lung, abdominal cavity, skin and soft tissue infection was higher than that in low-dose group, and there was a significant difference in the compliance rate between the 2 groups in pulmonary infection(P<0.05). With the increase of the minimum inhibitory concentration(MIC) of pathogenic bacteria, the PK/PD compliance rate decreased significantly in the 2 groups. A total of 7 adverse reactions occurred in 45 patients. There was no significant difference in the incidence of adverse reactions between the 2 groups. CONCLUSION Tigecycline is safer in critically ill patients. Higher doses shall be given when tigecycline is used for pulmonary infections and skin and soft tissue infections, especially pathogenic bacteria with high MIC.