Abstract: Objective :To study the expression of cytokeratin 19 (CIA 19), cytokeratin 20 (CIA 20) in periphery blood of patients with gastric cancer and its clinical significance. Methods :The expressions of CK19, CK20 in periphery blood samples from 66 patients with gastric cancer, 7 patients with benign diseases of digestive system and 21 healthy volunteers were detected by with FCM. Results :In blood samples from 7 patients with benign digestive diseases and 21 healthy volunteers, no expression of CK19, CK20 was detected (0/28). In blood sample from 66 patients with gastric cancer, positive expression rate of CK19 was 53.1% (35/66), positive expression of CK20 was 56.1% (37/66), positive expression of CK19 and CK20 was 46.9% (31/66). A significant difference (P<0.01) was found in the expression of CK19 and of CK20 between samples of patients with stage and I-III (TNM method). No significant difference was found in samples of patients with stage I-II< .The difference was significant between samples of patients with distant metastasis and no metastasis. The diagnosis of metastasis is high sensitivity (90%) and low specificity (60.71%). Conclusions :The Expression of CK19 and CK20 in periphery blood of patients with gastric cancer may be helpful in the selection of clinical treat and judgment of prognosis.