Objective To investigate the late diagnosis of HIV infection and associated factors in Jiading District between 1998 and 2022， and to provide the information for the development of AIDS prevention and control strategy.

Methods Information of newly reported HIV/AIDS cases in Jiading District between 1998 and 2022 were obtained from the National Information System for Comprehensive AIDS Prevention and Control. Logistic regression was used to explore the associated factors of late diagnosis of HIV infection.

Results In total， 809 HIV/AIDS cases was newly reported， 324 of which were late diagnosis with the overall rate of late diagnosis of 40.1%. Despite an increased tendency from 2016 to 2018， the rate of late diagnosis showed a downward trend from 1998 to 2015. The late diagnosis rate was 29.5% in 2015. From 2016 to 2022， the average rate was 34.9%. The average age of cases with a late diagnosis was 44.8±14.6 years old. Age groups over 50 had the highest risk，at 57.7%， accounting for 35.8% of all cases of late diagnosis. All age groups older than 30（OR=1.37‒3.50） had a higher rate of late diagnosis than the group between age 21 and 30. In comparison to patients at VCT clinic， the rate of late diagnosis among sexually transmitted disease （STD） outpatients （OR=2.23， 95%CI：1.42‒3.49） and other clinical patients （OR=2.75， 95%CI：1.88‒4.01） was higher.

Conclusion The late diagnosis rate of HIV infection is relatively high in Jiading District. AIDS education and prevention activities should be strengthened among people aged over 50 years. For early detection of HIV infection， VCT clinic platform’s function should be fully utilized. Medical institutions should pay attention to HIV testing in patients.