A mold clamp mechanism for a tire press with upper and lower molds, the clamp mechanism including a plurality of rod locking holes formed around the press center of the upper and/or lower mold; a corresponding plurality of clamp rods vertically received in rod receptacle holes in a fixed mold support structure, each clamp rod having a T-shaped head portion protrudable into a locking hole in the mold and lockable therein when the clamp rod is turned a 90 degree angle; a drive cylinder having rod operating arms connected to the piston rod thereof for movements toward and away from the clamp rod; rod rotating members mounted on the clamp rod and on one of the rod operating arms and engageable with each other when the piston rod is advanced toward the clamp rod to turn the same a 90 degree angle; and rod pull members mounted on the clamp rod and the rod operating arms and engageable with each other when the piston rod is further advanced toward the clamp rod after a 90 degree angle of rotation so as to clamp the mold to the fixed mold support structure.