Objective:To explore the curative efficacy of tandem autologous stem cell transplantation (ASCT) for high-risk multiple myeloma (HRMM).Methods:From January 2017 to December 2021, retrospective analysis was conducted for 240 initially diagnosed HRMM patients. According to different treatment protocols after induction chemotherapy, they were further assigned into three groups of tandem ASCT (n= 20) ,single ASCT (n=80) and non-transplantation (n= 140). Rates of deep response (very good partial response and above) before and after transplantation and differences in 2-year progression-free survival (PFS) and overall survival (OS) were compared among three groups. The prognostic factors of HRMM were examined by univariate and multivariate analyses.Results:In single ASCT group, the rates of deep responses were 67.50% (54/80) after induction chemotherapy and 80.00 % (64/80) post-ASCT ( P=0.072). There were no significant statistical differences. In tandem ASCT group, the rates of deep response were 65.00% (13/20) after induction chemotherapy and 95.00 % (19/20) post-ASCT ( P=0.018). There were significant statistical differences. The 2-year PFS of tandem ASCT, single ASCT and non-transplantation groups were (75.00±2.90) %, (71.25±3.00) % and (61.43±3.10) % respectively. No statistically significant difference existed in 2-year PFS rates between single ASCT and non-transplantation groups, as well as between tandem ASCT and single ASCT groups ( P=0.365 and P=0.052). Significant difference existed in 2-year PFS between tandem ASCT and non-transplantation groups ( P<0.032). Two-year OS rates of tandem ASCT, single ASCT and non-transplantation groups were (90.00±3.50) %, (78.75±2.70) % and (62.86±2.50) % respectively. No statistically significant difference existed in 2-year OS rate between single ASCT and non-transplantation groups, as well as between tandem ASCT and single ASCT groups ( P=0.071 and P=0.057). Significant difference existed in 2-year OS between tandem ASCT and non-transplantation groups ( P=0.003). Univariate and multivariate analyses indicated that the independent prognostic factors affecting PFS were multi-hit, stages RISS-Ⅲ and failure to achieve very good partial response (VGPR) after four cycles of induction therapy and non-tandem ASCT. The independent prognostic factors affecting OS were multi-hit, stages RISS-Ⅲ and non-tandem ASCT. Conclusion:Tandem ASCT not only significantly improves the depth of remission but also further enhances 2-year PFS/OS of HRMM patients. It is a recommended treatment for HRMM.