The Chief Minister is seeking re-election from Ampati constituency in South West Garo Hills, which he has been holding since 1993.
After filing his papers, Sangma told reporters that he was confident that the ruling Congress would get a clear mandate in the election as the focus of his government had always been on development.
Denying the allegation of P A Sangma-led National Peoples' Party that Congress was the reason for instability in the state, he said the government tried to address backwardness and poverty so that there would not be "any scope for instability".
More than 150 candidates have filed their nomination papers for the elections till today.