To solve the problems of poor crushing effect and uneven scattering of banana straw crusher in Hainan Province during operation, a field returning machine was designed with a biomimetic serrated grinding knife with good straw crushing performance. Applying the principles of bionics to the design of crushing blades, a biomimetic serrated crushing knife was designed based on the serrated profile of blue shark teeth. The cutting ability of the biomimetic serrated knife on banana straw was verified through simulation, and a mixed use of the biomimetic serrated blade and traditional crushing knife was designed. An experimental plan was developed for machine simulation and field experiments. Using Fluent flow field analysis software, the effects of parameters such as the speed of the crushing blade shaft, the height of the crushing chamber from the ground, and the distance of the crushing blade tip from the casing on the pressure and velocity fields at different positions in the banana straw crushing and returning machine during operation were studied. When the spindle speed was 2000r/min, the feeding characteristics of the crushing chamber were the best. The higher the height of the crushing chamber from the ground was, the better the feeding characteristics of the straw were, but too high or too low of the height from the ground can lead to a decrease in the fluidity of the straw in the crushing chamber. Increasing the gap between the tip of the crushing knife and the casing can have a negative impact on the scattering of straw. Through simulation and field experiments, it can be concluded that the combination of biomimetic serrated blade and traditional crushing blade can ensure the straw picking ability while improving the crushing qualification and scattering uniformity of the entire machine. The research result can provide support for the design and optimization of banana straw returning machines.