A mold core includes first and second main bodies and an adjustment assembly. The first main body includes a front surface, a rear surface opposite to the front surface, and a receiving cavity passing through the front and rear surfaces. The front surface defines two first cavities at opposite sides of the receiving cavity. A connection line of centers of the first cavities intersects with a symmetry axis of the first cavities to form a first intersection point. The second main body includes a forming surface defining second cavities. A connection line of centers of the molding cavities intersects with a symmetry axis of the second cavities to form a second intersection point. The forming surface is coplanar with the front surface. The adjustment assembly abuts the first and the second main bodies to compensate an offset between the first and second intersection points to satisfy a predetermined range.