Abstract: Aerospace and other industries with tough operating demands extensively utilize three-dimensional braided C/SiC composite threaded pipes as high-performance connection components. Evaluating their connection strength and damage processes is critical for assuring structural dependability and service life. This work extensively explored the mechanical response and damage processes of these composite threaded pipes through connection strength testing and multi-scale simulation analysis. A multiscale FE model for the connection strength of 3D C/SiC composite threaded tubes was developed based on yarn diameters, interfacial thicknesses, and mesoscopic unit cell dimensions obtained from SEM and Micro-CT. The experimental and computational data both show that the load-displacement response starts out linearly rising, with a stiffness of 14.11×10^6 N/mm on average and a maximum load of 35.94 kN. Notably, the damage displacement is significantly more than the screw thread height, roughly 3.31 mm. Due to the uneven load distribution among the threads, the threaded tube exhibits a sequential thread failure mode during loading, which further results in a distinct double-peak feature in the load-displacement curve. Primary damage occurs at the thread roots, where tensile-shear failure appears by the collective fracture of fiber bundles accompanied by partial fiber pull-out, while the matrix experiences brittle crushing. These findings give essential theoretical insights and technical assistance for the optimum design of threaded pipes.