Objective: In order to study the structure evolution of three states of powder, masterbatch and film of starch during extrusion blowing. Methods: Using hydroxypropyl distarch phosphate as raw material, starch film was prepared by extrusion blow molding. Using Fourier Infrared Spectroscopy-Attenuated Total Reflectance （FTIR-ATR）, X-ray Diffraction （XRD）, Thermal Stability Analyzer （TGA）, Gel Permeation Chromatography （GPC） and other technical means, crystal structure, thermal stability and molecular structure changes of the starch were analyzed in powder state, masterbatch state and film state. Results: After extrusion, the starch crystal form changed from powder state A to masterbatch state and film state V, and the derived peak intensity of the film state sample increased compared with the masterbatch state; the degradation of starch molecules resulted in the relative molecular mass at the same time, and the moisture content and solubility of the three-state samples show different trends. Conclusion: In the extrusion blow molding process, the high temperature and high shear of the extruder promote the interaction between the film-forming components and destroy the molecular structure of starch.