Objective:To evaluate the efficacy and tolerability of the dual therapy of dolutegravir (DTG) plus lamivudine (3TC) as a switch simplified strategy in treatment-experienced human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) patients.Methods:Treatment-experienced HIV/AIDS patients who switched to a dual therapy containing DTG (50 mg, once daily) plus 3TC (300 mg, once daily) were included in Beijing You′an Hospital, Capital Medical University from September 2016 to May 2019. HIV RNA, CD4 + T lymphocyte count, blood lipid indexes, renal function indexes were collected when patients changed the treatment regimen (baseline) and after 48 weeks of treatment. Efficacy (HIV RNA<50 copies/mL) and safety of the dual therapy were analyzed. Statistical comparisons were performed using the Wilcoxon matched-pairs signed rank test. Results:The reasons for 33 patients switching the treatment regimen were virologic failure (four cases, 12.1%), simplification of regimen (11 cases, 33.3%), and drug toxicity (18 cases, 54.5%). The patients were treated with anti-retroviral therapy (ART) for 2.13 (1.05, 4.23) years before regimens switching. Twenty-nine (87.9%) patients were virologically suppressed at baseline, and four (12.1%) patients were virological failure. After switching to DTG plus 3TC, all 33 patients showed HIV RNA<50 copies/mL after 48 weeks of treatment. The baseline CD4 + T lymphocyte count was 543 (363, 595)/μL. After switching the treatment regimens for 48 weeks, CD4 + T lymphocyte count was significantly increased to 625 (455, 651)/μL, and the difference was statistically significant ( Z=3.14, P=0.002). Compared with baseline, low-density lipoprotein-cholesterol was increased after 48 weeks of treatment (2.35(1.80, 3.08) mmol/L vs 3.12(2.74, 3.87) mmol/L), while triglyceride (2.21(1.27, 4.37) mmol/L vs 1.61(1.20, 2.22) mmol/L), the ratio of total cholesterol to high-density lipoprotein-cholesterol (5.02 (4.13, 6.40) vs 4.70 (3.55, 5.35)) and estimated glomerular filtration rate (106.4(78.2, 118.2) mL/(min·1.73 m 2) vs 88.6 (75.7, 107.9) mL/(min·1.73 m 2)) were decreased. The differences were all statistically significant ( Z=4.89, 2.37, 2.09 and 2.83, respectively, all P<0.050). No patient discontinued due to adverse events. Conclusions:The use of dual therapy containing DTG and 3TC is effective and well-tolerated in treatment-experienced HIV/AIDS patients under any prior ART without significant adverse events.