Abstract: Objective To investigate the prevalence of delayed HIV/AIDS diagnosis in Dali from 2012 to 2018 and its influencing factors. Methods Totally 4 648 HIV/AIDS cases whose current address was Dali were selected to analyze the prevalence of delayed diagnosis and its influencing factors. Results The prevalence rate of late HIV/AIDS diagnosis in Dali from 2012 to 2018 was 31.56%.Log-binomial regression analysis showed that delayed diagnosis rate was higher in male (PR=1.18,95% CI:1.07-1.30) than in female,higher in over 30 years old group than in other groups below 30 years old,higher in Han nationality (PR=1.13,95% CI:1.02-1.25) than in Bai nationality,higher in injection drug transmission (PR=1.28,95% CI:1.13-1.46) than in heterosexual transmission,higher in medical institutions (PR=1.15,95% CI:1.02-1.30) was higher than in voluntany counselling and testing. Conclusion It is necessary to expand the scope of testing and strengthen the education of HIV active testing.