Abstract: Objective To analyze the effect of muscle relaxant in the treatment of AIDS complicated with pneumocystis pneumonia in invasive mechanical ventilation. Methods Forty-three AIDS patients with pneumocystis pneumonia in our hospital from January 2015 to June 2017 were divided into treatment group (22 cases, muscle relaxant + routine treatment) and control group (21 cases, routine treatment), according to different treatment methods. The oxygenation index and airway pressure of the two groups were observed before and at 6 hours, 24 hours and 48 hours after treatment. The patients were followed up for 6 months, and the complications and survival of the two groups were compared. Results In the treatment group, there were 18 male patients, with average age of (43.6±12.4) years, the APACHE Ⅱ score was (23.2±4.4) and oxygenation index was (90.0±12.6) mmHg. In the control group, there were 17 male patients with average age of (40.8±10.7) years, and the APACHEⅡ score was (24±4), and the oxygenation index was (89.7±12.4) mmHg. Repeated ANOVA analysis of oxygenation index showed that there was an interaction between time and treatment, the oxygenation index increased by time in two groups (F=17.13, P=0.000), and it increased greater in treatment group than in the control group (F=15.14, P=0.000) (T48, 188.8±37.6 mmHg vs 167.2±20.3 mmHg, P=0.025).Interaction between time and treatment was detected for airway pressure (F=1.46, P=0.024). It decreased over time(F=2.48, P=0.013)and was lower in the treatment group than in the control group (F=49.31, P=0.000) (T48, 21.0±4.5 cmHg vs 24.4±6.3 cmHg, P=0.047). The complication rate in treatment group was significantly lower than the control group (14.3% vs 63.6%). After treatment, there were significant differences in occurrence cases of man-machine confrontation (2 vs 8, P＜ 0.05) and air pressure injury (1 vs 6, P＜ 0.05) between two groups, while no statistically significant difference was found in mortality (7 vs 10, P＞ 0.05) between the two groups during the hospitalization of ICU. Conclusion Muscle relaxant can improve oxygenation and airway pressure in patients with AIDS and pneumocystis pneumonia when invasive mechanical ventilation is applied.