Hospital is an important place for HIV/AIDS screening, and a general hospital is composed of multiple departments. Different departments have different levels of understanding of HIV/AIDS, especially the sexually transmitted diseases (STD) department is the main place for HIV/AIDS screening. The study aims to validate the common knowledge that the STD department is an important place for HIV/AIDS screening by comparing the epidemiological characteristics of HIV/AIDS patients in the STD department and other departments in Tongji Hospital, which can provide a theoretical basis for the precise and differentiated control of HIV/AIDS. A total of 283,525 HIV screening cases were analyzed from January 1st 2006 to December 31st 2018 in the STD department and other departments. The epidemiological data of 226 HIV/AIDS cases were retrospectively analyzed. Firstly, the incidence of HIV/AIDS in the population served by Tongji Hospital was higher than that in Shanghai and China. Secondly, the positive rate of HIV screening test in the STD department was ten times higher than that of other departments. Thirdly, the social-demographic characteristics of HIV/AIDS patients in the STD department were different from those in other departments. Fourthly, there were differences in age, education, marital status and number of sex partners between men who have sex with men (MSM) and men who have sex with women (MSW). Fifthly, there was no difference except age in social-demographic characteristics of MSM between the STD department and other departments. Sixthly, compared with other departments, the majority of HIV/AIDS patients in the STD department were MSM. Seventhly, syphilis and HIV co-infection were not statistically significant in HIV/AIDS patients between the STD department and other departments. Firstly, the significantly higher positive rate of an HIV screening test in the STD department emphasizes its importance as a place for screening HIV/AIDS patients. Secondly, HIV/AIDS patients diagnosed in the general hospital were mainly transmitted by sexual contact, and MSM accounted for the most part of these patients. More attention should be paid to screen outpatients, especially in the STD department and young men.