Abstract: Through the computational and experimental analysis on the modal of C/SiC ceramic matrix composite bolted fastenings, the modal parameters and vibration response characteristics were determined. The influence of tightening torque on the vibration performance of bolted fastenings was researched by sine-sweep vibration of the C/SiC ceramic matrix composite bolted fastenings. The influence of liquid polyborosilazanes (L-PBSZ) on the looseness-proof performances of C/SiC ceramic matrix composite bolted fastenings was measured. The results indicate that the first and the third natural frequency of the calculating modal are consistent with that of the experimental modal, so the finite element analysis method can be used for the vibration response characteristics analysis of C/SiC ceramic matrix composite bolted fastenings. The spectrum signal difference curves of sine-sweep vibration can be used to determine whether fasteners come loose or not. The ceramic fillers is observed between the screw pairs of L-PBSZ modified C/SiC ceramic matrix composite bolted fastenings by SEM, and the effective friction coefficient and the effective friction area increase with the nut and the screw, so the loose exit resistance of nut increases, and the looseness-proof performances of C/SiC ceramic matrix composite bolted fastenings are improved.