Abstract: Biodegradable aqueous polyurethane was made from self-made polyester diol. With varied proportions of lactic acid/adipic acid in the structure of polyester diol, the effects on the size of particle, hydrophilicity, biodegradability of polyurethane emulsion were studied. As the proportion of lactic acid increased, the particle size of the emulsion had a minimum. When the content of lactic acid was 25%, the hydrophilicity of the film made by polyurethane emulsion was the best; and as the content of lactic acid increased, the biodegradability of the aqueous polyurethane tended to increase.