The basic issue of a subject is the logical beginning point,from which the subject construct its theoretical system . There exist different opinions on the basic issue of ethics in China’s ethical circle .So it’s necessary to analyze and argue the basic issue of ethics again. Using the primary basic point of Marxism ——Practical Point, this article analyzes the basic issue of ethics under the guidance of the principle of Marxist Philosophy. And then there comes a new idea: We should consider the relationship between the ethical relation and the moral ability as the basic issue of ethics.