Umar bin Khattab was the first person to make a regulation separating executive power and judicial power. The regulation is known as 'Risala al-Qadha' whose contents contain several legal principles which basically refer to the principles of justice, Risala al-Qadha which is the thought of Umar bin Khattab is one of the proofs that Islam left civilization of high value and also proves that Muslim intellectuals have thoughts that lead to the future. This paper aims to analyze the concept of risalatul qadha Umar bin Khattab; know ijitihad ever done by Umar bin Khattab; and knowing the contribution made by Umar Bin Khattab to the Islamic justice system. This study is a qualitative study with a type of library research. The results of the study show that the important points of the qada treatise 'are: Justice is an obligation that must be obeyed; Judges must be fair; The judge reconsidered his decision, Ijtihad Umar bin Khattab in the field of justice; do not punish the cutting off of hands for perpetrators of theft, do not throw away adulterers who are still girls, while the contribution made by Umar Bin Khattab is to make the court an independent institution, giving the judiciary a special authority. Umar was also the first to appoint regional judges who had high independence and autonomy.