Objective　To explore the effect of GAS MAN assisted instruction on theory learn-ing of volatile anesthetics in anesthesiology residency training. Methods　A total of 32 residents in the first stage of anesthesiology training were enrolled and randomly assigned to either study（S） or control（C） group. Theory-test 1（Test-1） was conducted for all residents after the lecture-based learning（LBL）. Next， reference book self-reading strategy was used in both groups while computer-based simulation（CBS） using GAS MAN was only developed in S group. Then， theory-test 2（Test-2）was conducted for residents in both groups and residents in S group completed the questionnaire survey. In addition， thirty-four resident teachers observed the CBS courses and completed the questionnaire survey. Results　The mean scores of Test-1 did not differ significantly between the two groups（P=0.64）. However， the mean Test-2 score of S group（81.3±13.6） was significantly higher than that of C group（61.3±15.4）（P=0.001）. 100%（16/16） residents believed that CBS was beneficial to the theoretical study of volatile anesthetics， 93.8%（15/16） residents considered GAS MAN could help understand the concepts and improve efficiency during self-learning. 97.1%（33/34） and 91.2%（31/34） resident teachers agreed that CBS was helpful for analyzing complex concepts and improving study effectiveness， respectively. Conclusions　CBS using GAS MAN improves theory knowledge and study effectiveness for anesthesia residents. Both residents and resident teachers find GAS MAN highly ac-ceptable. Therefore， GAS MAN has the potential to be the assistant teaching tool for LBL in anesthe-siology residency-training program.