Abstract: Descartes’ ethics is a set of ethical theory based on the rationalist epistemology with the purpose of achieving human happiness, which is mainly composed of the three core elements: human reason, free will and habitual connection between body and mind. From the perspective of contemporary Western ethics, on the one hand, Descartes’ ethics contains the value theory which does not belong to the theory of interest or hedonism but to the perfectionism; on the other hand, it also contains the action theory which explains the appropriate actions. The three most influential theories in contemporary Western ethics are utilitarianism, deontology and moralism. Descartes’ ethics does not belong to any of them. It belongs to the tradition of Western classical happiness theory, to be more precise, it is a rationalist theory of happiness. Compared with the later ethical theories, Descartes’ ethics is quite simple. However, human reason as its core element is the starting point of modern thinking, which has profoundly influenced and even shaped the entire Western modern philosophy. It influenced the world and will continue to influence the world. That’s why it is still worth thinking about it.