Abstract: China is a big agricultural country with rich straw resources. Making good use of straw resources can greatly solve the problem of animal feed shortage, and also greatly solve the environmental problems caused by straw burning. Based on the analysis of the working mechanism of the straw extruder, the key components of the straw extruder screw and cavity are designed. For solving the problem of feeding blockage in extruder, the velocity flow field, eddy viscosity flow field and working pressure flow field of the outer cavity of screw are analyzed by means of ANSYS Workbench fluid module without replacing the motor. According to the calibrated production target, the test verifies that when the gap between screw and sleeve is 5 mm, the structure of straw extruder can achieve the expected production efficiency, and the quality of straw puffing is good. The straw extruder studied in this paper has changed the palatability of straw, and changed the crop straw with poor palatability into palatability feed.