AbstractIn this article, five kinds of straws were used to do compressing molding experiments on stress relaxation by Electric Versatile Material Machine, with specially designed open mode equipment. According to the data from the transition stage of the compression process, regression equations with different straws were built by selective global fitting or piecewise fitting. In addition, the equations were verified by stress logarithm-time curves. A stress relaxation model of the five straws can be summarized by an expression involving the summation of exponential decay terms. This expression provides reference for reducing the specific energy consumption and increasing the pellet density.