Dr. Sun Ya-b-Sien grasping our traditional spirit of benevolence and thought of social economics, appreciating the evils of an advanced environment, set up the Principle of the Livelihood of the People, in which the methods and maintenances offered to solve and prevent from our social problems, strongly revealing the thought of social welfare. Chiang Kai-Shih, the late president, succeeded in explaining and enlarging the social welfare thought of the Principle of the Livelihood of the People, not only making its contents more concrete and complete, but also making such a thought a set of systematic and complete system. The study of this thesis is devided into four parts, first of all, the formation of the factors of such a thought is made a thorough investigation. Secondly, the contents of the thought is talked about. Thirdly, the priceless value of the thought is talked of. At last, the practice of the expected value of the thought is pointed out.