Rituximab, a chimeric anti-CD20 monoclonal antibody, has been proved valuable treatment for CD20-positive DLBCL. The combination of rituximab with CHOP has been shown to increase both survival and response rate, in comparison to CHOP alone. CMAB304(Retuxira), a biosimilar of rituximab, was developed by Shanghai CP Guojian Pharmaceutical Co.,Ltd. Previous Phase I study showed that CMAB304 was well tolerated as monotherapy and the pharmacokinetic data exhibited a non-linear profile over the dose range of 250 to 500 mg/m2. In this study, efficacy and safety of CMAB304 were evaluated in DLBCL patients.