Modern medicine constructing with quantitative method in the paragon of natural science and technology is directly referred to the good health of human life nowadays under a certain degree of the superiority of precision and universal necessity. Facing the variation of human life itself, it is hard to diagnose precisely, despite the fact that medical science has brought great benefits to human. There is still full of "uncertainty." Although medicine scientized by natural science and technology benefits to human unprecedentedly, it leads to alienation of person from her/his being. The author takes a view from Mohists in ancient Qin Dynasty to propose love without-distinction as the core of practicing idea and "Standards" and "Three Tests" as the rules of practice to transform people’s experience from uncertainty of precarious living to achieve a certainty of common welfare. The paper attempts to learn from Mohists' practices in ancient Qin Dynasty and to think about transforming the method of Mohism in contemporary society in order to solve the uncertainty and person's alienation from her/his being in medical science. It is the "situation constructing" that indicates an important element among the solutions and it will be found as a clue in the method of Mohism.