Aiming at the problem of dock repair of semi-submersible ship and other heavy-duty products while strength of dock floor is insufficient,we analyze numerical simulation of the interaction between dock floor and steel case board under dock load by using finite element method,and study the influence of the spread of the load along the steel case board on the internal force and settlement of the dock floor.Contact problems between two different materials of concrete and structural steel can be well solved by the application of contact elements by the finite element method.The results show that there is no excessive intrusion,disengagement or slip between the steel case and the base plate.By setting the steel case board at the local position of the dock floor where large load is applied,the vertical load spreads along the four sides of the steel case board to extend the application range of the dock floor,which can effectively reduce the internal force and settlement of the dock floor.The method can effectively solve the problem of insufficient strength of dock floor.