Abstract: In order to research the yieldable characteristics of U-steel support, both the theoretical analysis and laboratory tests were used to study the yieldable condition and law based on the mechanical characters of the overlapping part of the U-steel support, and its influencing factors were analyzed. The results show that: The contact force between U-steel supports decreases gradually from the clamp installing position to the two sides of the steel, the farther from the clamp installing position, the smaller the contact force; The yieldable process of U-steel can be divided into three stages, including elastic compression stage, small slippage stage and sliding stage. In small slippage stage ,U-steel mainly overcame the friction effect and small displacement is occurred. But a larger displacement is occurred in sliding stage with a smaller axial force changing. The steel’s anti yieldable capacity will increase with the increase of pre-tension, but decrease with the increase of distance between the clamp and the applying force part. In the filed applications, the anti yieldable capacity of U-steel support can be enhanced by increasing the torque of clamps, increasing the number of clamps near the applying part, and changing the installing position of clamps.