The load capacity in composite mechanical joints with different fit conditions was investigated both experimentally and numerically. The analysis results show that the load capacity of composite mechanical joint structure increases at first and then decreases with the increase of the interference fit; the stiffness of the structure presents the same tendency with the interference fit increasing; the interference fit can also affect the failure mode of the composite mechanical joint and too large an interference fit can lead to a sudden failure. Adequate interference fit could improve the contact conditions around the bolt hole and result in a better load capacity of the composite joint structures.