Abstract: The present invention provides use of mitoxantrone hydrochloride liposome and pegaspargase in preparation of drug for treating NK/T-cell lymphoma (NKTCL). The NKTCL comprises initial-treating, relapsed, and refractory extranodal NKTCL. Preferably, the initial-treating, relapsed, and refractory extranodal NKTCL is initial-treating, relapsed, and refractory extranodal nasal NKTCL. On this basis, other first-line and second-line drugs for treating NKTCL can also be further used. The present invention further provides a method for treating NKTCL. The method relates to administering therapeutically effective amounts of mitoxantrone hydrochloride liposome and pegaspargase to a patient. The mitoxantrone hydrochloride liposome improves the curative effect of pegaspargase on NKTCL, has little toxic and side effects, and increases the complete response rate (CR rate) and the partial response rate (PR rate) of diseases.