The invention discloses a fixed compression hydraulic tire forming vulcanizer and a method for using the same. A compression hydraulic cylinder of the vulcanizer is an annular hydraulic cylinder; a cylinder barrel is fixed on an upper beam of an enclosed host machine frame; the lower end of a force transfer guide post is fixed on a vulcanizing chamber, and the upper end of the force transfer guide post passes through the annular hydraulic cylinder and the upper beam of the host machine frame; central lines of the force transfer guide post, the annular hydraulic cylinder and the host machine frame are superposed with one another; a mold locking mechanism is fixed at the front end of a piston rod of the annular hydraulic cylinder and ascends and descends along with the piston rod; the force transfer guide post is provided with 2 to 4 positioning grooves; and a slide block, which can move horizontally, of the mold locking mechanism is matched with the positioning grooves of the force transfer guide post. In the method for using the vulcanizer, the force transfer guide post descends along with the vulcanizing chamber during vulcanizing; the slide block of the mold locking mechanism is inserted into the positioning grooves of the force transfer guide post after appropriate mold closing, so that the force transfer guide post is fixedly connected with the piston rod of the annular hydraulic cylinder; and the annular hydraulic cylinder supplies pressure needed by tire vulcanizing. The width of the host machine frame is reduced and cost is lowered; centering accuracy is high; and a hydraulic seal is not damaged easily.