The carbon loss ratio of coke increases with increasing the coal rate injected in blast furnace and the strength of coke decreases with increasing the carbon loss ratio. To research the stress distribution in a blast furnace is the first step of the research on the limitation of coal rate for ironmaking. Based on element balance and general differential equation, a 2D mathematical model for simulating the stress distribution in a blast furnace has been established using equation of continuity, equation of motion and equation of state. The flow function and stress function have been deduced using difference equation. The program was designed using Microsoft Visual C++ according to the given boundary conditions of flow and stress fields. The calculation of the stress distribution is drawn.