Abstract: Ultimate bearing capacity of foundation should be calculated before penetration of Jack-up Rig to predict the penetration depth of Jack-up Rig footing. In actual work, it is calculated with the classical formula of ultimate bearing capacity which assumed soil as homogeneous foundation. However, for complex multilayer foundation, it is necessary to modify the calculation results because the mechanical properties of soil in the range of affecting depth of foundation have not been considered. The Finite Element Method has been used to simulate the failure mode of foundation and calculate the comprehensive ultimate bearing capacity. With the Finite Element Method, it is not necessary to modify the calculation results because the mechanical properties of soil in the range of affecting depth of foundation have been considered. Results show that the difference of properties of soil within foundation affecting depth range is the main factor of different failure mode and different bearing capacity. Full consideration should be given to 3.5 times the base size within the depth of all the mechanical properties of soil, the comprehensive bearing capacity is more consistent with the actual situation.