The invention discloses an assembly type building. The assembly type building comprises prefabricated wall plates, a laminating plate, a cast-in-situ slab and a tightening mechanism, wherein the upper end of the outer surface of each prefabricated wall plate is provided with a first groove; the lower end of the outer surface of each prefabricated wall plate is provided with a first bulge which is matched with the corresponding first groove; first holes are respectively formed in each first bulge and the corresponding first groove; a first bolt is arranged in each first bolt; the upper end and lower end of the inner surface of each prefabricated wall plate are respectively provided with a second groove; the two second grooves of the two adjacent upper and lower prefabricated wall plates are buckled into a containing groove; the tightening mechanism comprises a fixing plate and a second bolt; the adjacent prefabricated wall plates are fixed by the tightening mechanism; a bearing part is arranged at the end part of the overlapping plate and is matched with the containing groove. The assembly type building has the advantages that by matching each first bulge and the corresponding first groove, the problem of pouring of rainwater into the building via the gap between the two adjacent prefabricated wall plates is solved; the end part of the laminating plate is matched with the structure of the containing groove, so that the connecting between the laminating plate and the prefabricated wall plate is more compact.