This paper Studies the Nigerian system of administration after decades of colonial rule by the British empire. The primary administration laid in Nigeria is a combination of civil and military rule, and the early development and creation of new institution and a young democracy. Nigeria is one of the solid democracies in Africa as well as one of the countries to earn independence by the mid of the 20^th century. With facts seen, its proved Nigerian system of government in the post-colonial era is something that resembles institutionalization and strive for a new system of government and rule of law. Looking at the first republic system, to introduction of democracy, establishment of parliament, election, law and the enacting of new constitution with new orders and legitimacy. Nevertheless, Nigeria’s system of Government after the British colonialism is a spectrum that deserves a look back to understand what takes a turn and at what point.