The invention belongs to the field of building facilities and provides a method for controlling jointing of an external wall of a shear wall through three-section water stop screws. The method is suitable for reinforced concrete shear walls and frame structure external walls constructed through traditional timber formworks, and is characterized in that the three-section water stop screws are pre-buried in a lower-layer concrete slab, and used for fixing tight contact between the root inner surface of a formwork on the outer side of the external wall and the lower-layer concrete surface when a formwork is erected on the upper layer. According to the method, screw heads can be unscrewed and screwed on freely, and the formworks are convenient to dismount; when the formworks are dismounted, the screw heads can be unscrewed, and formwork dismounting is not affected; when the formworks are mounted, the screw heads are screwed on, and operation is simple and convenient; and the quality problems of mortar leakage, slab staggering and the like can be effectively avoided.