The long-term stress relaxation behavior and joint performance of prestressed timber joints were investigated experimentally and analytically. Our findings were as follows. By applying prestress in the fiber direction of LVL and compressed wood, we discovered the possibility of maintaining high pre-stress even under harsh environmental conditions. It was also found that the load factor, which is the ratio of the increase in the bolt axial force to the external load, is an important factor in the evaluation and design of joining performance.