The paper aimed to leveling operation of offshore jacket platform, studied mechanics principle of the leveling tool. When the clamp blocks inserted into the pile wall in leveling operation, the pile’s surface presented some indentations of elastic-plastic deformation, which can increase the cross-lifting force but the clamp is susceptible to be damaged certainly. So, special clamping block was designed including its material and mechanical structure, and force analysis of the pile under the action of the clamping blocks was finished, and dynamics simulation of contact process between the clamping block and the pile was finished too. An experimental prototype was developed to verify the clamping principle. Experimental results show that the clamping principle is correct and the leveling tool can meet actual needs.