A liquid-cooled heat radiator kit is disclosed to include a heat radiator, which has radiation elements at the top wall and parallel grooves at the bottom wall, two liquid-cooled heat pipes bilaterally arranged in parallel at the bottom side of the heat radiator, each liquid-cooled heat pipes having two close ends and a plurality of enclosed chambers spaced between the two close ends, and a plurality of straight flow-guide pipes respectively fastened to the grooves at the bottom side of the heat radiator and connected between the two liquid-cooled heat pipes to form with the enclosed chambers of the liquid-cooled heat pipes a detoured flow passage for the passing of a cooling fluid in one direction.