As a result of the “April 26 National Assembly Election” in 1988, out of a total of 299 seats, the Democratic Justice Party of Korea won 125 seats while 70 seats for the Party for Peace and Democracy, 59 seats for the Democratic Party got, 35 seats for the Republican Party, and one seat for the Hankyoreh Democratic Party. Nine seats were assigned to nonpartisan representatives. For the first time since party politics settled in Korea, the ruling party has failed to secure a majority of seats. The political situation of the so-called “Minority Government(the ruling party is small and the opposition party is large)” was formed.
 Under the Minority Government, neither the ruling nor opposition parties could solve anything independently, including passing the bill, and the bill could only be passed if the ruling and opposition parties agreed through discussions and compromise. That period was the most efficient operation of the National Assembly in Korean constitutional history. It was the heyday of so-called “political cooperation”. At that time, cooperation was operated correctly in the ruling and opposition parties' political affairs, allowing them to make breakthroughs in political, diplomatic, and national defense fields such as the “Inter-Korean Basic Agreement”, “Two Koreas’ Simultaneous Joining of the U.N.”, and “Clearance of the Fifth Republic Corruptions”. The ruling and opposition parties' political situation, which was formed from the 13th National Assembly election, was an opportunity for the Korean constitutional process to change into a process of communication and compromise with the opposition parties, not a unilateral dominance of the ruling party. The merger of the three parties is attributed to the desires of the President and the ruling party to secure leadership in national affairs and the opposition leaders who led the merger. The merger of the three parties during Roh Tae-woo's regime has resulted in distrust of party politics and destabilization of the Korean party system, including the merger of political parties according to their interest and the production of migratory politicians in each election.
 This paper aims to analyze the achievements of political cooperation made under the Minority Government since the inauguration of the Roh Tae-woo government in 1988, and the achievements of the “Three-party Merger” made thereafter in terms of constitutional history.