The aim of this paper is to make full use of the hydroxyl groups on the ground tire rubber (GTR) surface to realize the high valuable utilization of waste tires in the field of high-performance polyurethane elastomers. In this work, the Polyurethane/Ground tier rubber (PU/GTR) thermoplastic composite with excellent performance was in-situ synthesized by adding untreated GTR to polyurethane. With incorporating 3.44 wt% GTR to polyurethane, the tensile strength of the PU/GTR thermoplastic composites was improved by approximately 166.7 % compared with pure PU. And the dynamic heat generation index (ratio of the tan δ at 90 °C and 30 °C) of the thermoplastic composites was reduced to 0.97, being far lower than that of pure PU (1.62), which exhibits this material has low dynamic heat generation when subjected to alternating stress. As expected, X-ray photoelectron spectra (XPS) results showed that the GTR indeed participated in the in-situ synthesis of polyurethane, thus, resulting in the GTR particles with micro size being evenly distributed in the polyurethane matrix via a network structure, which was proved by the morphology analysis and rheological measurement part. Additionally, the microphase separation of the PU matrix of the composites was greatly weakened according to Cole-Cole plots and the small angle X-ray scattering (SAXS) analysis. And the outcome of the study provided a low-cost and rational approach for recycling of waste tires while avoiding resource waste.