The invention discloses a lower-portion grouting device and method for concrete shear wall displacement. The lower-portion grouting device comprises a connecting sleeve, an upper clamping plate fixedly sleeving the upper portion of the connecting sleeve, a base plate located under the upper clamping plate and capable of vertically moving on the connecting sleeve, a spacing piece located under the base plate and used for spacing the base plate and an exhaust pipe mounted on the outer side of the upper portion of the connecting sleeve and communicated with the interior of the connecting sleeve; the upper portion of the connecting sleeve penetrates a molding template in a bottom-up manner, and the upper clamping plate and the base plate form a clamping structure; the upper end of the exhaust pipe extends out in a bottom-up manner to the position above a shear wall to be displaced, and the lower end of the connecting sleeve is connected with a grouting pipe; a backflow prevention piece is arranged on the connecting sleeve; the lower-portion grouting method includes the steps of 1), division of sections to be displaced; 2), reinforcement through lower-portion grouting. The lower-portion grouting device and method is reasonable in design, easy to operation and good in use effect, the shear wall at the position of the floor can be grouted easily and rapidly from below without opening holes in the floor or the wall above.