The invention discloses a lengthening joint containing a prefabricated concrete-filled
steel tube core column component and a construction method of the lengthening joint. The lengthening joint comprises an upper-section core column, a lower-section core column, a steel reinforcement framework, a joint concrete layer and out-of-tube concrete
layers. The bottom end of the upper-section core columnis connected with an upper
flange plate, the top end of the lower-section core column is connected with a lower
flange plate, a connecting
assembly comprises a connecting plate, bonding glue
layers and high-strength bolts, the connecting plate is arranged between the upper
flange plate and the lower flange plate, air holes are formed in the middle of the plate face of the connecting plate at intervals, the bonding glue
layers are arranged between the connecting plate and the upper flange plate and between the connecting plate and the lower flange plate, and the upper-section core column and the lower-section core column are connected through the high-strength bolts; and the steel reinforcement framework is arranged around joints of the upper-section core column and the lower-section core column, and the joint concrete layer is poured between the out-of-
pipe concrete layer on the outer side of the upper-section core column and the out-of-
pipe concrete layer on the outer side of the lower-section core column. The technical problems that the thickness of an existing joint cannot be adjusted, inclination deviation exists, compression deformation is large, force transmission is not reliable, construction efficiency is low, and concrete in a steel
pipe is difficult to pour are solved.