Objective:To investigate the drug-resistant mutations of human immunodeficiency virus-1 (HIV-1) in patients who received highly active antiretroviral therapy (HAART) from 2014 to 2018.Methods:A total of 880 patients with HIV-1 infection who had been treated with HAART for more than six months in Chongqing Infectious Disease Medical Center from May 2014 to December 2018 were enrolled. Plasma samples were collected, and one-step reverse transcription-polymerase chain reaction (PCR) and nested PCR were taken to amplify protease and reverse transcriptase regions of HIV-1 pol gene region. The obtained amplified nucleotide sequences were compared with the drug resistance database for antiviral drug resistance analysis. Viral genotyping tool software was used to analyze HIV-1 subtype distribution. The categorical variables were compared using chi-square test. Results:Among 880 patients, the plasma HIV-1 viral load was (4.12±0.63) lg copies/mL, the CD4 + T lymphocyte count was (251±124)/μL, and the median duration of antiviral therapy was 26 months. In the subtypes analysis, the circulating recombinant form (CRF) 01-AE subtype was the largest proportion of HIV-1 subtypes, accounting for 38.9%(342/880), and the CRF07-BC subtype accounted for 28.5%(251/880), B+ C subtypes accounted for 16.2%(143/880). Drug-resistant mutations were detected in 534 patients, with a total drug resistance rate of 60.7%. The drug resistance rates of nucleoside reverse transcriptase inhibitors (NRTI), non-nucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI) were 51.0%(449/880), 58.6%(516/880) and 1.7%(15/880), respectively. The drug resistances to lamivudine, emtricitabine, efavirenz, and nevirapine were serious, and the medium/high resistance rates were 46.8%(412/880), 46.8%(412/880), 51.3%(451/880), and 53.6%(472/880), respectively, while those to zidomidudine (6.0%, 53/880), etravirin (9.0%, 451/880) and PI were not serious. M184IV (47.3%), K65R (22.2%) and K70RE (12.6%) were the most frequent mutations for NRTI. K103NS (25.1%), V106A (19.7%) and V179DE (14.4%) were the most frequent mutations for NNRTI. The most common drug-resistant mutations for PI were L10FIV (7.4%) and A71IVT (6.5%). The drug resistance rate of CRF01-AE subtype (69.3%, 237/342) was higher than those of CRF07-BC subtype (49.8%, 125/251) and B+ C subtype (51.0%, 73/143), the differences were statistically significant ( χ2=22.6 and 14.6, respectively, both P<0.05). Conclusions:The incidence of drug resistance is high among HIV-1 infected patients after six-month HAART treatment in Chongqing City. The drug resistance to NNRTI is the most common, followed by NRTI, while PI is less resistant. Drug resistance is the main reason for the virological breakthrough in HIV-1 infected patients.