Self-elevating drilling units are one of the mainstream equipment for offshore oil and gas exploration and development. Windlass foundation structure of a JU2000E self-elevating drilling unit is selected as a sample, the finite element modeling method and detail is introduced through its strength analysis. Analysis and check is done to make ensure that its strength meets the requirements of classification society rules as well. The job also provides direction for subsequent structural strengthening and optimization design. The method introduced here can also be referred by the strengthening analysis of other mechanical equipment based on hull structures.