Geopolymers are an important class of materials with potential applications because of their heat resistance, flame resistance, environmental friendliness, and possibilities of being transformed into ceramic matrix composites at low cost. However, the low mechanical properties as well as the intrinsic brittleness limit their technological implementations, and it is necessary to enhance the mechanical properties of geopolymers by adopting various kinds of reinforcements. In this work, therefore, two-dimensional continuous carbon fiber ( Cf ) reinforced phosphate-based geopolymer composites ( Cf/geopolymer ) were prepared through ultrasonic-assisted impregnation method. Effects of acetone treatment and high-temperature treatment on the properties of Cf/geopolymer composites were studied by X-ray photoelectron spectroscopy ( XPS) , X-ray diffraction ( XRD) , and scanning electron microscopy ( SEM) . Results of the study proved that acetone treatment plays a key role in ameliorating the interfacial interaction between Cf and phosphate matrix, which can thus enhance the mechanical properties of Cf/geopolymer composites. The Cf/geopolymer composites prepared by acetone-treated Cf had a flexural strength of 156. 1 MPa and an elastic modulus of 39.7 GPa in Y direction. Moreover, an additional Sol-SiO2 re-impregnation treatment could further enhance the mechanical properties of the acetone-treated Cf/geopolymer composites by repairing the cracks and filling the pores. The results in this paper not only provide insights into the surface modification of Cf , but also report a facile and low-cost preparation route for Cf/geopolymer composites with potential applications in aerospace and defense technology.