The invention relates to a prefabricated building and a component anchoring method thereof, and belongs to the field of buildings. The prefabricated building is composed of a prefabricated wallboard, a cast-in-place anchoring beam, a cast-in-place concrete beam, a cast-in-place concrete constructional column, a cast-in-place concrete column, a cast-in-place concrete floor, a raft (strip-shaped) foundation, a window (hole), a column main reinforcement, a beam main reinforcement, a beam stirrup, a cast-in-place anchoring beam main reinforcement, a hollow pipeline, an anchoring steel bar and other components. The component anchoring method comprises the following steps of anchoring the cast-in-place concrete beam, the cast-in-place anchoring beam and the cast-in-place concrete column on the prefabricated wallboard, wherein notches are reserved in the upper and lower ends of the prefabricated wallboard, and anchoring steel bars are reserved on the side vertical surfaces; and anchoring the cast-in-place concrete beam, the cast-in-place anchoring beam and the raft (strip-shaped) foundation or the cast-in-place concrete floor at the two ends of the cast-in-place concrete constructional column on the prefabricated wallboard. The problems of long construction period, high cost, serious material waste and many potential safety hazards of construction of a traditional building are solved, and the problems of difficulty in anchoring a filler wall of the prefabricated building, infirmness in anchoring and poor corrosion resistance are also solved.