Abstract: Natural starch did not possess the characteristic of thermoplasticity and could not be processed in plastics machine. The molecular structure must be disordered in order be thermoplastical. After plasticized by two-step approach it possessed the probability of thermoplastic process of starch. Biodegrable all-starch thermoplastics were made of thermoplastic starch as the main raw material. And the performance testing and characterization were carried out. It has broad application prospects due to its low cost and good performance.