The invention discloses a fixing device for an LED tunnel lamp. The fixing device comprises an LED lamp body and a mounting plate; four connecting holes are symmetrically formed in the plate face of the mounting plate, connecting screws connected with the top of a tunnel are arranged in the connecting holes, a mounting protruding part is arranged at the bottom of the mounting plate, and first annular parts are arranged at the bottom of the mounting protruding part; mounting sliding grooves are formed in the left side and the right side of the mounting protruding part, connecting supports are in sliding fit with the interiors of the mounting sliding grooves in the two sides, and the bottoms of the two connecting supports are fixedly connected with the LED lamp body; three or more heat dissipation metal strips are arranged on each of the two connecting supports, and inserting grooves allowing the heat dissipation metal strips to penetrate are formed in the connecting supports; and the heat dissipation metal strips are used for increasing the heat dissipation area, and therefore heat dissipated by the LED lamp body is absorbed and is rapidly dissipated.