Objective To investigate the relationship between locus of control, mental resilience and fatigue among military personnel. Methods Internality, powerful others, and chance (IPC) scale, Conner-Davidson resilience scale (CD-RISC) and fatigue scale 14 (FS-14) were used to investigate locus of control, mental resilience and fatigue among 553 soldiers, respectively. Structural equation model was built to analyze the relationship between variables. Results There were 532 valid questionnaires and the effective response rate was 96.2%. There were no significant differences in locus of control between soldiers with different demographic factors including only-child or not, residence before entering army or complete structure of natal family (all P>0.05), but significant differences were found in gender and education level (senior high school or below vs university or above) (both P<0.05). For fatigue, there was significant difference in gender (P<0.01), but no significant difference in other demographic variables (all P>0.05); soldiers with low internal control (high external control) scored higher in fatigue than those with high internal control (low external control). The 3 dimensions of locus of control, 3 dimensions of mental resilience and 2 dimensions of fatigue were all correlated with each other significantly (all P<0.01), except correlation between internality and physical fatigue. Locus of control and mental resilience were able to explain 22.8% of the total variation of fatigue. The results of mediation model and Bootstrap test presented that mental resilience mediated the relationship between locus of control and fatigue among military personnel (χ²/df=4.888, goodness of fit index=0.983, adjusted goodness of fit index=0.940, normed fit index=0.983, relative fit index=0.957, incremental fit index=0.986, Tucker-Lewis index=0.966, comparative fit index=0.986, root mean square error of approximation=0.086). The total mediation effect of mental resilience was 22.58%. Conclusion Mental resilience partially mediates the association between locus of control and fatigue. We should pay more attention to fatigue of soldiers who tend to be externally controlled, help them improve mental resilience, reduce their fatigue, and enhance their work efficiency.