In this paper, Moso bamboo is the main object to study its radial compression mechanical properties of bambooculm by ring stiffness method. It was found that the optimum length of samples was its outer diameter. The ring stiffness of Moso bamboo was 80-180 kN/m2, far greater than QB/T 1916-2004 standard given in the SN16 level. Ring stiffness increased with stem height from bottom to top, but declined after 4-year-old. Bamboo joint can improve the radial compression of bamboo-culm，and that with bamboo joint was about 2.30 times of without. Using hose clamps can improve the strain of bambooculm, but the holes reduce its radial compression performance with the increase of hole diameter. Therefore, it is inferred that ring stiffness can be used as a novel and reliable method for assessing the radial compression mechanical properties of bamboo-culm.