The purpose of this multi-center,single arm,phase Ⅱ clinical trail is to determine the safety and efficacy of Chidamide with R-GemOx(rituximab、gemcitabine plus oxaliplatin) regimen in the treatment of transplant-ineligible patients with relapsed/refractory diffuse large B-cell lymphoma.

Inclusion Criteria:

• biopsy proved CD20+ DLBCL;
• relapse or refractory DLBCL#
• previously received systemic chemotherapy with anthracycline#
• not eligible for autologous hematopoietic stem cell transplantation#
• at least one evaluable lesion#
• ECOG PS 0-1;
• 18-75 years; without other malignancy;
• proper functioning of the major organs.

Exclusion Criteria:

• double-hit lymphoma;
• previously received treatment of HDAC inhibitor;
• plan to receive autologous stem cell transplantation;
• involvement of central nervous system;
• previously received gemcitabine within the past 6 months;
• patients who received treatment for hematologic toxicity caused by previous chemotherapy within 7 days before enrollment;