The invention discloses an assistant for a car tyre dismounting-mounting machine and a manufacturing method of a main part. The assistant is a structure characterized in that one mechanism drives two mechanisms. A vertical performer is connected to a sliding body, the upper end of the sliding body is hinged to an upper tyre-pressing mechanism, and the lower end of the sliding body is hinged to a lower tyre-pressing mechanism. A guide rail plate is installed on a stand column so that a combined guide rail is formed. The guide rail plate is a 45# bar-shaped steel plate and has linearity and flatness less than or equal to 0.05mm/m. The stand column utilizes a rectangular steel tube as a bending-resistant beam, upper part, lower part and sides are respectively welded with bosses as stand column installation reference surfaces, and flatness is less than or equal to 0.1mm/m. Upper and lower stoppers and first and second transverse bars are welded to the sliding body with an inner slide block, and the sliding body is connected to a piston rod of the vertical performer by a spherical plain thrust bearing. The lower end of the performer is hinged to the bottom of the stand column by a hanging trunnion. Upper and lower yaw guide sleeves are provided with hook-shaped wrenches. A console comprises a handle, a front panel welded assembly, a rear cover plate welded assembly, a basin-shaped cone gasket and sunk screws. After rough and fine processing, the combined guide rail, the sliding body and the console can be assembled to corresponding parts. The assistant has the advantages of structure characterized in that one mechanism drives two mechanisms.