The study will start with an initial 2 cycles of induction therapy with CAGM containing chidamide, azacitidine, obinutuzumab and mitoxantrone liposome, orelabrutinib and rituximab,following imaging examinations to evaluate response rates. For patients feasible to CAR-T/ASCT, sequential CAR-T/ASCT treatment was given. For patients who were unable to undergo CAR-T/ASCT, 4 cycles of CAGM immunochemotherapy were carried out. Efficacy and safety of CAGM regimen in R/R DLBCL will be evaluated.