Abstract: Objective To study the infectious diseases-related factors in fever of unknown origin(FUO). Methods Five hundred and three patients(454 were diagnosed with FUO) admitted to our department from December 2009 to December 2011 were retrospectively analyzed. The 454 cases were divided into infectious disease group and non-infectious disease group. Their infectious diseases-related factors were analyzed by univariate and multivariate logistic regression analysis, respectively. A logistic regression model was established. Results Univariate and multivariate logistic regression analysis showed that arthralgia, course of disease, weight loss, ALP, SF, and neutrophils(N) were the infectious diseases-related factors. Their regression equation:Logit(p)=12.707-1.613× arthralgia- 0.016× course of fever- 0.878× weight loss- 0.011×ALP- 0.001×SF-0.097×N. The area under the ROC curve was 0.857 9. The optimal cut off value was 2.32, the sensitivity was 68.35%, and the specificity was 89.33%. Conclusion Arthralgia, curse of fever, weight loss, ALP, SF and N are the infectious diseases-related factors. The area under the ROC curve is 0.857 9, the sensitivity is 68.35%, and specificity is 89.33% in logistic regression model.