In a statement, the Qatar Football Association said: "We're currently on the look-out for a new coach. We thank Mr Belmadi for his services and co-operation.
"We got some very good results in his stint as coach. He was one of our finest coaches.
"He lifted the spirit of the players and carried out his tasks well."
Belmad looked to be on the right track with Qatar since his appointment in March 2014 by winning the Gulf Cup of Nations in November but then finished bottom in Group C of the Asian Cup in January.
Qatar start are grouped with China, Bhutan, Maldives and Hong Kong in the 2018 World Cup and 2019 Asian Cup qualifying.