Objective To study the enzymatic degradation processes of P(3HB-co-4HB) . Methods The physical properties and biodegradability were evaluated by mechanical properties test, weight loss, TGA, XRD and SEM. Results The results showed that the presence of 4HB units improved the roughness of the materials, and decreased their brittleness. The degradation rate of 4 materials decreased in the order P(3HB) > P ( 3HB-co-5% 4HB) > ( 3HB-co-10% 4HB) > P ( 3HB-co-15% 4HB) . The thermal stability was slightly improved at the beginning of the degradation and then decreased. The results of XRD showed little difference in crystallinity in the process of enzymatic degradation. With the increase of the fraction of 4HB units,the surface of material became rougher, the surface of material was corroded after enzymatic degradation, and the degradation rate was consistent with the results of weight loss rate. Conclusion The presence of 4HB units remarkably influenced the mechanical properties of the materials, with the increase of the fraction of 4HB units, the weight loss increased, the thermal stability first increased and then decreased, the surface of materials got rougher, and the crystallinity had no change for the surface erosion in the process of enzymatic degradation.