Abstract: Objective : To discuss the expression of Rb, p16 and CyclinD1 proteins in large intestine carcinoma and its clinical significance. Methods The expression of Rb, P16 and CyclinD1 in the colon-rectal malignant carcinoma and normal mucosa were measured by flow cytometry (FCM) and all the data were analysed by SAS after the data were transformed to FI (fluorescence index). Results : a) FI(x±s) of Rb,P16 and CyclinD1 in the colon-rectal malignant carcinoma with FI (x±s) of normal mucosa are analyzed by T test (P0.01). b) The correlations between Rb, P16 and CyclinD1 and the degree of malignancy were further researched after the expression of Rb was classified, depending on whether the expression of Rb was positive or negative. When Rb was the positive expression, namely, Rb FI1.0, the expression of P16 will have a negative correlation with the grade of histology. CyclinD1 had a positive correlation with grade of histology. And less expression of P16 has a significant correlation with the lymphatic metastasis as Rb FI1.0 and above, P0.01. c) When the expression of Rb was negative, Rb had a negative correlation with lymphatic metastasis, P16 had a positive correlation with lymphatic metastasis and CyclinD1 had a negative correlation with lymphatic metastasis, P0.01. Conclusion : a) There are a significant difference in the expressions of Rb, P16 and CyclinD1 between colon-rectal carcinoma group and normal mucosa group. b) When the expression of Rb is positive, the inactivation, lost, or mutation of P16 will lead to more and more malignant and easily cause lymphatic metastasis. The degree of activeated CyclinD1 will lead to more and more malignancy. c) When the expression of Rb is negative, all the results indicate that negative feedback maybe affect the expressions of Rb, P16 and CyclinD1. But, owing to the only samples in 4 cases of this group, the results need more studies by enlarging the samples.