Abstract: Design rationality of cutting and crumbing device is a main factor affecting cutting quality，working performance and balance of straw cutting and kneading and bundling machine.Through research on density and arrangement of crushing cutter of cutting and crumbing device，simulation analysis of crushing cutter and cutter shaft by using SolidWorks Simulation analysis software，maximum stress of crushing cutter was got with 20.7 MPa，showed that crushing cutter has enough strength to support cutting of straw，modal vibration diagrams of cutter shaft were also got，that showed that actual working speed of cutter shaft is much lower than its minimum critical speed，which could meet needs of practical work.