Objective To study mechanical properties of the medical water-jet scalpel when cutting parenchyma such as liver and verify its tissue-selective cutting characteristic. Methods The tension mechanical properties of porcine liver parenchyma and its vessels with different sizes were determined. Porcine and Wistar rat liver tissues were cut with arteriovenous vessels well reserved, and pathological section of the rats were analyzed by HE staining to explain the experimental phenomena. Results When the working pressure was set at 3 MPa, the incising and separating on the right lobe of porcine liver by medical water-jet scalpel in this experiment were done with minimal vessels of 0.8 mm in diameter left. Pathological sections from ordinary scalpel and medical water-jet scalpel showed that the medical water-jet scalpel caused smaller tissue damage. Conclusions The medical water-jet scalpel could cut heterogeneity soft tissue with highly-selective characteristics, which may effectively avoid the existing “one size fits all” phenomenon caused by ordinary scalpel.