The utility model relates to a double variable speed component of exhaust duct, which is arranged inside an exhaust duct for speed-change of air flow, comprising a shell. A speed change hole and an air induct pipe for two air flow passages are arranged inside the shell; the speed change hole is an air flow speed change passage with different inside diameters; the inside diameter of the speed change hole air inlet is larger than that of the speed change hole at least one section above the speed change hole air inlet; a section of vertical straight hole is provided at the air outlet of the speed change hole; the air induct pipe comprises an air inlet and an air outlet; the air inlet communicates with the air outlet on the pipe wall of the exhaust duct. The air induct passage is of a kettle spout shape with an aperture gradually decreasing from an air inlet to an air outlet; the air outlet of the kettle spout shape air induct pipe is a section of vertical straight hole; and the straight hole connects with the kettle spout shape air induct pipe smoothly through an arch surface. The utility model has the advantages of simple structure, convenient installation, smooth fume exhausting, and prevention of fume return, fume and odor tainting.