Abstract: In order to evaluate the load bearing capability of thread teeth of C/SiC composite bolts, finite element method and stiffness degradation method were used to study the load bearing capability of the thread teeth of C/SiC composite bolts. The results show that when the number of teeth engaged is more than six, the initial pull-off load of thread teeth almost does not increase with the number of teeth engaged increasing, and it also can not be increased significantly by solely increasing the pitch of thread for this will decrease the initial pull-off strength of thread teeth; when the ratio of thread teeth to bolt diameter is constant, the initial pull-off load of thread teeth is proportional to the square of bolt diameter; however, the ultimate pull-off load of the thread teeth is nearly proportional to the number of teeth engaged, the pitch of thread and bolt diameter.