Constitutional monarchy is a national system relative to absolute monarchy. Constitutional monarchy is an ideal to establish people's sovereignty, limit the power of the monarch and realize the harmony of affairs without constitutionalism on the premise of retaining the monarchy. It can be divided into dual constitutional monarchy and parliamentary constitutional monarchy.

Britain's "glorious revolution" set a precedent for constitutional monarchy. Generally speaking, the monarch is lifelong, and by definition, the monarch's status is higher than other citizens of the country (this is a difference between the monarch and other heads of state, such as dictators). Often the monarch belongs to a special class (nobility), and hereditary system is often a feature of the monarch.

Although the monarch is the head of state, the way and scope of the monarch's power exercise will be different according to the systems of various countries; Even in the same country, in different times, the monarch's mode of production and scope of power are different. Constitutional monarchy is closely related to a country's national conditions and cultural traditions. It has made some progress, but there are also some compromises, backwardness and limitations.