Abstract: Abstract: Maize is one of the most important graincrops in the black soil region of Northeast China. Since the straw burning after harvest in autumn can lead to air pollution, the straw return-to-field has been widely used to cultivate the ground for the soil organic matter, further enhancing the yield and air environment. Most straw returning machines focus on only one independent operation, the same as the harvesters with straw returning devices. Current straw returning can easily cause straw congestion during no-till seeding in spring, and the amount of soil movement cannot easily retain the required moisture level, particularly when the straw is uniformly thrown to the ground or buried in the ground by rototilling. Alternatively, the monopoly furrow straw return can significantly increase the roughness of monopoly furrow to slow down the runoff velocity for the resistance to the sediment transport, further reducing the annual runoff coefficient and soil erosion modulus of the slope. However, there are only a few reports on the straw returning machine under the monopoly furrow straw return to the field. In this study, a straw breaking and diversion device was designed to smoothly introduce the cut straw into the field stage, in order to improve the straw crushing rate and straw congestion during no-till sowing in spring. Among them, a fixed blade and a high-speed moving blade were utilized to slice the maize straw in horizontal and longitudinal sections, and then the maize straw was guided along with the deflector to the field stage. A mechanical kinematic model was also established for the straw cutting and deflector during operation. The kinematic and kinetic analysis was combined to determine the influencing factors in the straw breaking and diversion device, including the distance of moving and fixed blade, deflection, and dip angle of the deflector. The results showed that the optimal combination of the parameters in the straw breaking and deflecting device was achieved, where the distance of moving and fixed blade was 48 mm, the deflection angle of deflector was 52°, and the dip angle of deflector was 45°. At the same time, the straw deflection rate was 93.8% in the straw breaking and diversion device, indicating an outstanding deflection. Furthermore, the qualified rate of straw crushing was 3.53% higher than that of the returning field device of flail blade, and 2.15% higher than that of the returning field device of hammer claw. Consequently, this device can effectively improve qualified rate of straw crushing, thereby reducing the straw cover on the field stage for less straw congestion during no-till seeding. This finding can provide a strong reference for the straw returning in maize harvesters.