Abstract: In order to realize nondestructive diagnosis and treatment of endoscope, to improve the walk ability of intestine robot, the structure and boundary lubrication models of intestine need establishing. The small intestine acted as the research object in the paper. We characterized the inner structures and determined the relationships between friction coefficient and diameter, load and sliding velocity. The results show that the small intestine inner structures consisted of plica, villus and micro-villus. The importance of the main factors affecting the friction coefficients were the diameter, the movement velocity and the load in the order. On the basis of inner structures and the variation of friction coefficient of small intestine, the structure and boundary lubrication model were established using the film theory. The lubrication regime was hydrodynamic lubrication when intestine was in contracts. The friction resistance was mainly determined by the shear strength of the mucus rather than load and sliding velocity. The lubrication regime was film lubrication when intestine expanded, and changing load and sliding velocity varied friction. The friction resistance mainly included the shear strength of the mucus, the mechanical resistance and the absorptive force.