Résumé
A traditional idea in our country is that birth is the beginning of a person, therefore when one comes to the world he becomes a person who is different from fertilized egg, embryo and fetus, But it doesn't point out what the real life entity is before it was born. The traditional idea in the west is that fertilization is the beginning of human being,therefore we can easily find the differences among fertilized egg, embryo, fetus and animal. But it does not point out the differences between the life entity before it was born and a person. The modern belief is that the person and human being, as well as animal can be differentiated from the point of ontological status and moral status. Therefore it has overcome the limitation of the traditional idea in both our country and the west, and established the theoretical foundation on how to do the research and solve the medical ethics problem.