A coldblooded killer was sentenced to 25 years in the slammer yesterday after helping the feds bring down the head of a notorious Chinese gang based in Queens.

Hoa Duc Nguyen, who turned rat after becoming the first fugitive extradited from China in 2003, admitted in Manhattan federal court to taking part in three murders for his mentor, Hui Sin “Frank” Ma.

Two of those killed were innocents mistakenly targeted during a botched 1994 hit on a Toronto drug dealer.

He had faced life before agreeing to a plea deal.