To study the restoring force model of recycled aggregate concrete filled square steel tube (RACFSST) frame, 6 frame specimens were designed and fabricated for low-cycle reversed loading tests. By analyzing the hysteretic and skeleton curves obtained from the tests, the skeleton curve model, hysteresis rules, and calculation method for unloading stiffness of RACFSST frame were clarified. Meanwhile, by comprehensively adopting the bearing capacity sudden drop treatment and the fixed-point targeting treatment method, the restoring force model applicable to RACFSST frame was established. The results indicate that the failure characteristics of the specimens include flexural-shear failure of RAC beams and column bases bulging. The overall failure mode of the frames satisfies the seismic design requirements of “strong column-weak beam” and “strong joint-weak member”. The hysteretic curves of RACFSST frames exhibit a full spindle shape, demonstrating that RACFSST frames have excellent seismic energy dissipation capacity. The load-bearing process of the frames consists of elastic, elastoplastic, and failure stages. The proposed tri-linear skeleton curve model and restoring force model have good agreement with the experimental results, and they can be used for elastoplastic seismic response analysis of this kind of structures.