According to the practical needs of mobility, flexibility and adaptability of paddy field lotus root digging machine, a crawler pontoon lotus root digging machine chassis was designed. The chassis was mainly composed of frame, walking device and detachable pontoon. The chassis frame of the lotus root digging machine was analyzed by finite element method, and the equivalent stress and overall deformation nephogram of the chassis frame were obtained. According to this, the weak and redundant parts were optimized. The dynamic simulation of its mobility was carried out based on ADAMS. The results show that the force between track chains changed about 30% and 10% respectively when turning and climbing, and the maximum rollover boundary angle was 38.6 °. The field walking performance test of the chassis was carried out. The results showed that the maximum output torque of the chassis hydraulic motor was greater than or equal to 740.44 N·m, the in-situ turning diameter was less than or equal to 2.5 m, the slip rate in the hard soil layer was less than or equal to 3%, the chassis was convenient to go up and down the field, walked stably, could climb the slope less than or equal to 25°, and the walking and trafficability could meet the design requirements. This study provided an important reference for the research on mechanized mining technology and equipment of lotus root.