Extranodal natural killer/T-cell lymphoma (ENKTL) is an aggressive subtype of non-Hodgkin's lymphoma and shows extremely poor survival. Several retrospective studies and randomized prospective phase 2 studies have shown that Peg-aspargase based chemotherapy regimens achieved a promising efficacy in the first line treatment of ENKTL. However, about one third of patients will relapse or become refractory after Peg-aspargase-based chemotherapy followed by radiotherapy, and some patients cannot tolerate the toxicities caused by chemotherapy. Anti-PD-1/PD-L1 antibodies and Chidamide are active drugs for the treatment of relapsed/refractory ENKTL. However, there is no prospective study to evaluate the efficacy and safety of anti-PD-1 antibody combine with Peg-asparaginase and Chidamide in the newly diagnosed early stage ENKTL. This prospective pilot study to evaluate the efficacy and safety of the anti-PD-1 antibody combine with Peg-asparaginase and Chidamide regimen for stage IE and IIE ENKTL.