The invention belongs to the technical field of plastic pipe machining and discloses an automatic cutting device for plastic hoses. Through the automatic cutting device, the cutting lengths can be set. The automatic cutting device comprises a rack, a material supporting guide rail, an electric push rod, an upper fixing mechanism, a lower fixing mechanism and a cutting mechanism. The material supporting guide rail and the cutting mechanism are oppositely arranged and fixed to the rack. The electric push rod and the rack are connected in a sliding mode. The bottom of the upper fixing mechanism is fixedly connected with the electric push rod. The bottom of the lower fixing mechanism is fixedly connected with the material supporting guide rail. The upper fixing mechanism and the lower fixing mechanism are of a symmetrical structure, fixed in a die-combining mode, and provided with mutually matched limiting grooves correspondingly. According to the automatic cutting device for the plastic hoses, overall fixation of the plastic hoses with different shapes and lengths can be achieved, meanwhile, according to the set cutting lengths, redundant materials at the two ends of the plastic hoses are cut fast, and the cutting precision and cutting efficiency are high.