As the starting point of thinking about ethical reasons, commensurability is not only the key to resolving disputes among various ethical reasons, but also an important dimension to exploring ethical practice. Whether the ethical reasons are commensurable or not is a basic issue concerned by the ethics circle. From the perspective of ethical motivation reasons and consequence reasons, they are incommensurable due to their characteristics. Although ethical reasons are incommensurable, it provides a new opportunity for people to study ethical issues and urges people to think about ethical practices.