To realize stable forming of the one-sided stitching (OSS) of the composite preform and avoid missing loop, wrong hooking and unstable stitch forming during the process of stitching the preform, the original OSS process is improved, and a wire-pulling mechanism which can realize the stable forming of the trajectory is added. The  mathematical model of the wire-pulling mechanism is established, and the trajectory of the end actuator of the wire-pulling mechanism is simulated and analyzed, which proves the rationality of its design. The working principle of each mechanism of the OSS device is analyzed. By determining the phase differences among the crank angles of the yarn-lifting, yarn-leading, yarn-hooking and wire-pulling mechanisms, the coordination relationship of the four mechanisms of the OSS device is analyzed and planned, and the motion cycle diagram of each mechanism is established, which lays a theoretical foundation for debugging of the OSS device. Finally, multiple controlled OSS experiments were conducted at varying parameters, including preform thickness, stitch pitch, and stitching speed. The result of loop formation rate of 100% proves the rationality and effectiveness of the motion planning, enhances the stability of the OSS trajectory, and thereby ensuring consistent stitching quality of the composite preforms.