The invention discloses a movable lamp housing fixing device. The movable lamp housing fixing device comprises a base plate; the base plate is arranged on one side of a tool plate; the height of the base plate is larger than that of the tool plate; a sliding rail is arranged on the base plate and provided with a movable base; the movable base is provided with a sliding rod; shock absorbers are installed at the two ends of the sliding rod; a fixing base for fixing a lamp housing is perpendicularly arranged in front of the movable base; locking rotary arms controlled by an air cylinder are arranged on the left and right sides of the fixing base; the sliding rod is further provided with a bolt installation base. As the fixing base fixes the upper end of the lamp housing, the movable base moves to a left tool plate body to machine a left lamp housing body and then a right lamp housing body is installed and moves to a right tool plate for right machining, the problems that the lamp housing machining cost is high and the machining efficiency is low in the prior art are solved.