Objective To study biological characteristics of R5 tropic human immunodeficiency virus (HIV)-1 strains in different disease stage. Methods Primary clinical viruses were isolated from fresh peripheral blood mononuclear cells (PBMC) using co-culture methods; meanwhile, viral co receptor usage and infectivity were tested using flow cytometry on GHOST (3) cell lines,which expressed CD4 receptor and CC ehemokine receptor 5 (CCR5) or CXCR4 eoreceptor; to identified CCR5 tropic viruses(R5 tropic strains). Viral replication kinetics was detected in PBMCs. Plasma viral load was measured using an HIV-1 nucleotide fluorescence quantification assay kit. Results There were 22 individuals with HIV-1 subtype B' infection, in which 11 were CD4>0. 2 × 109/L and 11 were CD4≤0. 2 × 109/L. All isolated viruses used CCR5 coreceptor and therefore were HIV-1 R5 tropic strains. The infectivity of R5 tropic strains isolated from patients with CD4≤0.2 × 109/L was (7.392 7 ± 4. 584 2) % ; while the infectivity of R5 tropic strain from patients with CD4>0. 2 × 109/L was (2. 613 6 ± 1. 610 5)%. There were significant statistical difference(t= 3. 262, P<0.05). The possibility of viral replication became strong after the day 7 post-infection. There was a significant difference of viral replication between two groups in the day 7,10, 15 post-infection(t value was 3. 771, 2. 509 and 2. 260 respectively, P<0. 05). The possibility of viral replication was higher in CD4≤0.2 ×109/L group than that of CD4>0.2 × 109/L group. The logarithm of viral load was (5. 606 8 ± 0. 815 1 ) copies/mL in CD4≤0.2 × 109/L group and (4. 729 8 ± 0. 431 6) copies/mL in CD4> 0.2 × 109/L group. There was a significant difference between two groups(t = 3. 771 ; P<0.05). Conclusion Viral infection and replication are enhanced during progression of disease, even if viral coreceptor usage do not switch from CCR5 to CXCR4.