Abstract: Objective To explore the expression of transporter associated with antigen processing （TAP） and major histocompatibility complex class （MHC）-Ⅰ molecule in malignant melanoma cell lines. Methods Three malignant melanoma cell lines, including A375, A875, and KZ28 cells as well as normal melanocytes were cultured. Western blot, reverse transcription PCR and flow cytometry were used to detect the protein and mRNA expression of TAP as well as the membrane expression of MHC-Ⅰin these cells. Results A significant decrease was observed in the expression of TAP mRNA （t = 5.89, 4.45 and 4.57 respectively, all P < 0.01） and protein （t = 5.46, 4.32 and 4.67 respectively, all P < 0.01） in A375, A875 and KZ28 cells compared with the melanocytes, with the strongest decrease occurring in A375 cells. Similarly, the expression of MHC-Ⅰ molecule was significantly lower in A375, A875 and KZ28 cells than that in the melanocytes （t = 6.16, 5.22 and 5.61 respectively, all P < 0.01）. Conclusions The protein and mRNA expression of TAP is down-regulated in three melanoma cell lines A375, A875 and AZ28, which may contribute to the escape of melanoma cells from human immune surveillance.