Double cantilever beam tests were used to measure the energy release rates of linear vibrational welded moso bamboo joints. The influence of the length of the preserved cracks, the different combinations of the inner and outer bamboo surfaces and the moisture content is studied herein. The experimental compliance method, which is based on linear elastic fracture mechanics and has been shown to be an ideal method, was used to analyze data with the power equation. The results show that the preserved initial crack length does not have a significant effect on the final measured energy release rate, while the moso bamboo combination does affect the properties dramatically. The welded moso bamboo joints with inner-inner surfaces have the highest energy release rate of 122 J/m2. The average energy release of the outer-outer combination was only 102 J/m2. The expansion of the cracks also became easier when the moisture content of the welded joints was 18.5% compared to 4.5% and 10.1%. So the moisture resistance of the welded joints should be duly improved.