The distribution of vertical additional stress of soft soil foundation with upper hard crust under uniform strip load is numerically simulated by finite element method. Through the simulation, the coefficients of interlayer vertical additional stress with different ratios of crust thickness to load width and ratios of crust modulus to soft soil modulus are obtained, and tables with these coefficients are given for reference. Furthermore, an approximate function of these coefficients versus ratio of crust thickness to load width and ratio of crust modulus to soft soil is presented using binary regression analysis. Finally, a calculation formula for vertical stress of soft soil foundation with upper hard crust is deduced based on the concept of equivalent depth, and the validity of this formula is verified by case calculation.