Concrete filled double-skin tubular structures （CFDST） that reuse waste steel slag demonstrate advantages in sustain? able resource use. The interaction and coordination between steel tube and concrete make CFDST an effective solution to the stabil? ity issues， considering the expansion characteristic of steel slag. The expansion performance of the steel slag concrete can enhance the bond between the steel tube and its sandwich concrete. This paper presents a series of tests on a steel slag CFDST T-Joint un? der pseudo-static loading conditions to investigate its seismic performance. Five specimens were tested， including one ordinary con? crete test specimen and four steel slag concrete test specimens. The variables tested were concrete type， hollow ratio， diameter ra? tio， and axial compression ratio. The results show that while the bearing capacity of steel slag concrete specimens is slightly lower than that of ordinary concrete， the displacement ductility and energy dissipation capacity significantly increased， by 69.46% and 48.20% respectively. As the hollow ratio increases from 0.3 to 0.5， the displacement ductility coefficient of the specimen increases by 9.69%. When the diameter ratio of branch main increases from 0.40 to 0.68， the displacement ductility coefficient increases by 82.44%. However， when the axial compression ratio increases from 0.1 to 0.2， the displacement ductility coefficient of the speci? men decreases by 17.98%. A finite element model was established to simulate the hysteretic properties of the specimen. The simu? lation results are in agreement with the test results， verifying the validity of the finite element model. Based on the verified finite model， the parameters of influencing factors on the bearing capacity of the specimen were analyzed， and the optimum hollow ratio of the specimen was found to be about 70%. The use of steel slag greatly improves the seismic performance of the CFDST T-joint and can be widely used in concrete-filled steel tube engineering structures.