To reveal the effects of spatial variation of soil on ultimate bearing capacity of a strip footing, the random finite element model (RFEM) based on Monte Carlo technology is presented, and is implemented by Matlab and ABAQUS. Then the model is applied to the analysis of the ultimate bearing capacity of a strip footing. The elastic modulus and cohesion of soil are considered as random spatial variables with the variation coefficient of 0.3 in this model, and 250 Monte Carlo simulations are conducted. The corresponding ultimate bearing capacity of foundation are obtained and probabilistic statistical analysis is performed. The results show that the spatial variation of foundation soil usually leads to the reduction of the ultimate bearing capacity. For the reliability of 90% and the variation coefficient of 0.3, the bearing capacity is 5.4% lower than homogeneous case.