The invention discloses a modification method of polybuthylenesuccinate. The method comprises the following steps: first, performing oxidative modification on cellulose microcrystalline to obtain dialdehyde cellulose; then under a certain condition, performing full and uniform mixing on the dialdehyde cellulose with polybuthylenesuccinate in a high-speed mixer; adding other components; performing further uniform mixing; performing granulation; and performing injection moulding to obtain a high-performance composite material which is modified polybuthylenesuccinate. The modified polybuthylenesuccinate has larger tensile strength, accordingly has a better mechanical performance and has a wide application prospect and wide market potential.