After the collapse of the Islamic caliphate, various forms of modern Islamic states emerged based on the nation-state. This fact becomes the background of the importance of conducting research that focuses on a comparative study of the differences in the constitutionality between Saudi Arabia and the United Arab Emirates. Both countries embrace Islam as an ideology with absolute monarchy and elected monarchy systems of government.  This qualitative research is sourced from literature studies, aiming to explain in a structured manner the differences in the state administration of Saudi Arabia and the United Arab Emirates. This study found that Saudi Arabia adheres to an absolute monarchy system of government with a unitary state form; the government system of this country is an absolute monarchy led by a king. In the government system, there are no elections, even if there are only for the election of legislative and judicial bodies; the executive body is also known as the "Council of Ministers of the Government of Saudi Arabia" which consists of the king of ministers and advisers to the king. Most Islamic citizens dominate the system because they are the king's descendants. At the same time, the Arab Emirates adheres to Islamic ideology in accordance with the Qur'an and sunnah, adhering to an elected monarchical government system with a federal state form of seven emirates. Most Muslims also live in the United Arab Emirates, where a Sheikh rules each emirate, and then together, they form the Supreme Federal Council. One of the Sheikhs serves as the head of state and the president, and Muslims also control the government system of this country, as Muslims also control the defense system of the UAE.