Abstract: Abstract :Objective 　The study was designed to investigate the effect of arsenic t rioxide (As₂O₃ ) on metastasis of nasopharyngeal carcinoma cell line HNE1-LMP1. Methods 　HNE1-LMP1 cells were cultured in the media containing 3μmol/ L of As₂O₃ for 48 hours and then recovered in the free drug media for following 48 hours. Af terwards, only the attached cells were collected to analyze its metastasis potential. Reconstituted basement membrane invasive assay was used to evaluate the ability of adhesion, migration and invasion in HNE1-LMP1 cells. Confocal microscopy was performed to observe the expression of latent membrane protein 1 (LMP1) . Results 　As₂O₃ significantly inhibited membrane adhesion and invasion as well as migration of HNE1-LMP1 cells. The expression of LMP1 was also reduced as demonst rated by Confocal microscopy examination. Conclusion 　As₂O₃ was a potential agent inhibiting NPC invasion and metastasis. The mechanism might be associated with the reduction of LMP1 expression.