Star-shaped polymer of epoxidized soybean oil (ESO) and lactide is a new material. Its degradation function has an importance to its applications. There are many factors affecting its degradation. This paper is mainly aimed at investigation in which the surface morphology, pH, molecular weight and weight loss rate, branching ESO-lactide star polymers the degree of change were studied. It was found through the experiments that, the changing rates of the branching ESO-lactide star polymers were slower than the degree of PDLLA change compared to the surface morphology, pH, molecular weight and weight loss rate. This has a guiding significance to the further application of ESO-lactide.