Myeloid-derived suppressor cells (MDSC) which suppress cytotoxic T-cell functions are expanded in tumors and contribute to tumor escape from immune surveillance. The interplay between tumor cells and MDSCs results in tumor growth, relapse, and metastasis. We have found that the expansion of MDSC in the peripheral blood and tumor tissues from nasopharyngeal carcinoma (NPC) patients, which linked to tumor metastasis and poor patient survival. To reveal the molecular mechanism responding to the MDSC expansion in NPC, we further investigate the crosstalk between NPC cells and myeloid lineage cells in a mimic tumor microenvironments in vitro. First, Our observations demonstrate that EBV-LMP1 antigen expression in NPC cells could promote the tumor-associated MDSC generation and differentiation through up-regulating glycolysis of NPC cells. The glycolysis of NPC cells promotes the production of IL-1 and IL-6 by activating NLRP3 inflammasome, leading to the expansion of cytokine-induced MDSC. Next, we found that immune regulatory protein Galectin-9 is up-regulated in NPC cells, the increase of tumor Galectin-9 is a predictor for poor survival of NPC patients and associated with MDSC expansion. Mechanical study reveals that Galectin-9 induces MDSC expansion by deactivating STING signaling pathway resulting in increase of p-STAT3 in tumor cells and myeloid cells. Totally, our study highlight the novel molecular mechanism mediated by Gal-9/STING/p-STAT3 axis responding for MDSC expansion in NPC, and provide the potent targets for NPC immunotherapy by inhibiting the expansion of MDSC.