Abstract: With the rapid development of thermoplastic composites, traditional sizing agents are no longer able to meet the requirements as its incompatibility with thermoplastic matrices and low heat resistance. In light of this, it is fairly significant to master the technologies of sizing agents suitable for high performance thermoplastic composites. Brief introductions including chief purposes of sizing treatment, strengthening mechanisms at the interfaces between reinforcements and matrices, distinguishing features as well as main requirements of carbon fiber sizing agents for thermoplastic composites were presented in this paper. Researches of novel carbon fiber sizing agents consisting of polyamide, polyurethane, polyaryl ether, polyimide and other constituents for various thermoplastic matrices were reviewed in the order of service temperature. Both modification routes of diverse sizing agents for high performance thermoplastic composites and commercial applications provided by carbon fiber manufacturers were presented with their relative merits and existing drawbacks. Furthermore, their corresponding mechanisms and development status were also clarified. Finally, the future trends of sizing agents for thermoplastic composites were forecasted with relevant suggestions provided subsequently in view of different sizing agents to overcome current problems.