Abstract: Exploring laws of cracking and propagation of walnut shell under impact force has good guiding significance for breaking through bottleneck of walnut shell breaking and kernel extraction equipment．Using walnuts from Tianmu Mountain area at border of Anhui and Zhejiang provinces as experimental materials, different shapes of punch heads were used to fabricate cracks, and their influence on crack initiation guidance was studied through simulation analysis．Trend and pattern of crack propagation was observed through baking tests．Based on experimental results, a walnut shell breaking machine was designed．Striking hammer head and fruit bowl groove of shell breaking component adopt a groove type structure with seven internal grooves, which enabled walnut to effectively guide cracks under impact force, facilitate separation of shell and kernel, and achieve better shell breaking quality．Prototype has achieved expected effect through testing, and its shell breaking material provided convenience for subsequent heating, vibration processing and other processes．