Extranodal nasal-type NK cell lymphoma (ENKL) is a high-grade malignancy and associated with EBV latent infection. An optimal therapy has not been discovery. Here, we investigated whether cell proliferation was inhibited by silencing Epstein-Barr virus nuclear antigen 1 (EBNA1) using RNA interference (RNAi) method in an EBV-positive ENKL cell line, HANK1 cells. We found that silencing EBNA1 expression by RNAi strategy inhibited cell growth and increased the expression of p27 protein and caused cell cycle arrest at G(1)-phase in HANK1 cells. In conclusions, low-level expression of p27 protein may partially attribute to latent EBV infection in ENKL. EBNA1 may be a good target for the treatment of EBV associated ENKL.