Abstract: Objective 　To detect the expression and significance of cell keratin (CK) in malignant melanoma. Methods 　To detect CK、Vimentin、S2100 、HMB45 in 18 cases of malignant melanoma using immuno-histochemical method-PV-9000 two steps. Results 　The positive expression rates of CK in 18 cases of malignant melanoma were 67%(12/18) ;among them, the positive rates of CK and Vimentin in 16 cases of primary melanoma were 63 %(10/ 16), 100 %(16/ 16) respectively ; the positive rates CK and S-100 、CK and HMB₄₅ were 50 %(8/ 16) respectively, the positive expression rate of the above four kinds of antibodies was 44 %(7/ 16) ; the positive expression rates of the four kinds of antibodies in two cases of metastatic melanoma were 100 %(2/ 2) . Conclusion 　There was positive expression in varying degrees of CK in primary and metastasis melanoma.