The assembly will consist of all members of parliament, for the purpose of deliberating, and seeking views and advice of the people on the new Constitution.
The assembly will also be preparing a draft of a Constitution Bill for the consideration of parliament.
Prime Minister Ranil Wickremesinghe had introduced the resolution first in December 2015, and it was to have been debated and passed on January 9, a day after the first anniversary of the victory of Maithripala Sirisena in the Lankan Presidential election.
The Speaker will be the Chairman of the Constitutional Assembly while seven others will be Deputy Chairmen.
The government had already set in motion a process to seek public views on the form of the new Constitution.
The new constitution will replace the current executive president headed constitution adopted in 1978.
PTI