The invention discloses a control tool for fabricated type building seam sealing and a construction method. The control tool comprises a sealing and blocking section, a hand-held section, a connectingsection and a removal limiting member, wherein the sealing and blocking section extends into a seam from outside to inside, the hand-held section is located in front of the sealing and blocking section and located on the outside of the seam, the connecting section is connected between the sealing and blocking section and the hand-held section, and the removal limiting member is arranged on the outer side of the rear part of the sealing and blocking section. The construction method comprises the steps that first, the tool is controlled to move in place; and second, the seam sealing construction is carried out, specifically, the control tool for fabricated type building seam sealing is adopted to divide the seam into a plurality of seam sections to perform seam sealing construction from back to front correspondingly. According to the control tool for fabricated type building seam sealing and the construction method, the design is reasonable, using operation is simple, the using effect is good, the inlet amount and the inlet distance of seam sealing materials entering the seam are limited by the sealing and blocking section limiting the seam sealing materials in the seam, and the grouting connection quality of a steel bar sleeve is guaranteed; and meanwhile, the seam sealing materials are not required to be smeared on the outside of the seam, the amount of the seam sealing materials can be effectively reduced, the construction cost is saved, the construction difficulty is reduced, the construction efficiency is improved, and sealing quality is improved.