A small sized metal-rubber part being vulcanized, the annular rubber surface is a curved surface with high inner and outer rings and a concave middle part, and such a product is not only out of keeping with the design requirements but also an affection of sealing performance. By measuring the protrusion amounts of the highest and lowest points of the rubber surface of the metal-rubber part relative to the metal end face and the concave amount of the rubber itself, the overall protrusion amount of the rubber surface is indirectly described. In this paper, the control variable method is utilized for conducting experiments from the dimensions of mold design, molding vulcanization process and stay time before measurement. It appears from these experiments that the mold molding surface designed to about R50 arc surface can effectively compensate the concave amount in the middle of the rubber surface, the thickness of the rubber blank is controlled at more than 130% of the design thickness, the vulcanization pressure is controlled at more than 6 MPa, the increasing pressure controlled at 40%~60%, and the stay before measurement is not less than 24 hours, ensuring the protrusion amount of the rubber surface for meeting the design requirements and the sealing performance. The experimental results show that thanks to the improvement of the design of the mold forming surface, adjustment of the size of the rubber blank, the vulcanization pressure and the pressurization rate, and prolongation of the stay time before measurement, it has become possible to effectively control the protrusion amount of the rubber surface of small sized metal-rubber parts.