The invention discloses a method for accurately weighing additive for an environment-friendly dry-mixed mortar stirring building. An additive weighing and correcting device is arranged, an additive weighing test system parallel to the additive weighing system is arranged, and the actual weight and the pressure error of an additive can be accurately weighed by using a scale on the ground, so that the error caused by vibration of a stirrer to the weighing amount is avoided, and a correction curve is obtained. The weighing error caused by vibration of the stirrer is further corrected through a controller, the accurate weighing effect of the additive weighing system is achieved, and the production quality of dry-mixed mortar is improved. Meanwhile, arrangement and work of the weighing and correcting device can be conducted when the dry-mixed mortar stirring building normally works, special shutdown is not needed, and the method is simple and convenient to operate.