An orthogonal cutting model for investigating indentation type cutting of soft tissue was established, and the cutting force model was constructed theoretically based on fracture mechanics. A planar biological soft tissue cutting experimental setup was designed and developed to realize soft tissue cutting. Cutting experiments using orthogonal cutting blades were performed on fresh porcine liver at different cutting speeds. It was experimentally shown that the cutting speeds and the blade rake angles have significant effects on the penetration force and cutting force. Finally, a regression equation was obtained to explain the relationship among cutting force, cutting speed, and rake angle. These findings provide new insight into the biological soft tissue cutting.