The flow path of the 250 singlescrew extruder with the maximum width of the extruded product reaching 1 600 mm is studied object. Based on the feedback from the field application, the original structure was analyzed. The optimal design was proposed under the influence of finite element analysis (FEA) of ANSYS-polyflow. The field production verification results show that the optimized design solution can solve related problems well，meet customers production requirements and achieve good application results.