Abstract: In order to explore the correlations between the molecular typing of canine mammary tumors （CMT） and the clinicopathological indicators of CMT and lay the foundation for the clinical diagnosis, treatment, and prognosis, in the report, the CMT samples were collected and the histopathological evaluation was performed, ER, PR, HER2 and Ki-67 proteins were used for molecular typing, and the correlations between the molecular typing and the clinicopathological indicators were analyzed. The results showed that 70% （49 cases） of CMT were triple-negative, 12.9% （9 cases） were Luminal A, 1% （1 case） was Luminal B, and 10% （7 cases） were HER2-enriched. Among them, the expression differences of ER （P=0.033） and Ki-67 （P=0.021） were significant between the normal breast tissues and the tumor samples, and the expression differences of Ki-67 were significant among the different tumor grades （P=0.007）, while there was no significant correlations between PR protein, HER2 protein, molecular typing and clinicopathological characteristics.