The rheological property of small intestinal mucus of dogs was studied, and the Casson's rheological model of small intestinal mucus of dogs was obtained in this paper. The results obtained indicate that small intestinal mucus is a kind of Non-Newtonian fluid. Its apparent viscosity decreases with increasing shear rate. When the shear rate is high enough, the apparent viscosity of small intestinal mucus becomes a constant. [WT5HZ]