This paper introduces the definitions, theories, schools, criticisms, and debates of consequentialism and utilitarianism. Two cases and theory of “quality adjusted life year (QALYs)” have been proposed as examples for demonstrating the application of consequentialism and utilitarianism in bioethics. A concise working formula for consequentialism is also presented. It is hoped that this paper will be a useful reference for medical students and health care professionals for their understanding of an important ethical theory and be helpful for their clinical ethical reasoning. (Full text in Chinese)