Polyurethane foam has many excellent features such as thermal insulation and shock and sound absorption, and is used for refrigerator parts, car parts and many other products. Simulating the precise behavior of polyurethane foaming is very effective for reducing the development period and production costs. Through experiments and foaming flow simulations, in this study it was found that for a given foaming condition, the maximum flow length of polyurethane foaming increases in proportion to the foaming weight, while the specific volume change with time is constant for all foaming weights. A foaming flow simulation was then developed by applying density and viscosity formulated as functions of elapsed polyurethane foaming time to a 3D flow simulation program. This foaming flow simulation allows precise determination of the foaming flow length, and the tendency and maximum pressure of foaming flow.