Death is a human issue. Since the beginning of human life, this issue has had a deep connection with the thought system of philosophers and has become a basic concept in the thought of thinkers. For this reason, different interpretations of this concept have been made in philosophical schools. Plato and Sadra have provided reflections on this concept. By examining the works of Plato and Sadra, we find out that in the works of these two philosophers, another death called voluntary death is planned along with natural death, which is realized by human effort and creating a separation between soul and body. It seems that this concept has a deep connection with knowledge and ethics in the thought of Plato and Sadra. The main issue of this article is to deal with what voluntary death is and to examine the ruling relationship between this concept and knowledge and ethics in the thought of Plato and Sadra. The writer is trying to analyze the concepts of what was said by comparative analysis and in a descriptive-analytical way. The result of the present research shows that in the eyes of these two philosophers, voluntary death, knowledge and ethics have a single function. The importance of these ancient writings is that the abstract state of the metaphysical concepts of the philosophy of Plato and Sadra is explained in the form of concrete concepts such as death and morality.