Abstract: Abstract: In the main grain crop production in China, comprehensive mechanization level for paddy field is the lowest. At the same time, there exists the "bottleneck" problem of "bottleneck" problem such as rice planting mechanization. In the case of transplanter, although we have grasped the core technology of key components, overall machinery can not be popularized and applied due to lack of the support of cost-effective chassis. At present, in Chinese market, most of chassis are imported from Japan and South Korea, which widely use hydraulic transmission and variable speed technology. Because paddy planting operation has the characteristics of stable load and constant speed, using hydraulic transmission and continuous variable device causes low efficiency and has no much practical significance, and meanwhile, the demand for the power increases from 9 to 13 and even 15 kw. Northeast Agricultural University has designed a standard all-wheel drive light paddy self-propelled chassis with diesel-power and mechanical transmission for this situation, whose most prominent shape feature is that four wheels have same size and the front axle is different from any existing paddy field chassis structure. The chassis has the advantages of high transmission efficiency, large torque reserve, anti-sink capacity, dynamic stabilization, and good performance of crossing the earth bank between the paddy fields. As a transmission part, steering drive axle not only is a carrier installed, but also needs to bear the weight of chassis and the effect of impulsive load, and have the function of deflection wheel, and hence its structure is more complex than the traditional shell. The operating environment of paddy field chassis is harsher than general vehicle, which has stricter requirement of sludge, subsidence, bank and over load on axle. So, engineering analysis of structural design process is particularly important, however, conventional theoretical analysis and calculation method can not accurately control the stiffness and strength in the process of structural design. For this situation, the research utilized CATIA finite element analysis module to build the finite element analysis model with connection relationship and force transferring characteristics on the three-dimensional model of axle housing, and according to the working condition features of chassis and mechanics analysis, divided every section of the grids and imposed constraints and load boundary conditions; through the analysis of axle's limit load according to the ground adhesion, it was drawn that the drive force of front axle was 1 143.4 N, and the supporting load was 2 430 N, which met the actual requirement of vehicle application environment and ensured the scientificity and effectiveness of engineering analysis data. The deformation and stress of the axle were respectively 0.218 mm and 121 MPa through theoretical analysis and finite element calculation. The engineering structure of steering drive axle met the design requirements, and the deformation met the relevant standards after the test of experiment and trial installation. The research first makes the standard all-wheel drive paddy chassis, which takes the lightweight and high-passage as the goal, come into the stage of comprehensive performance verification, providing not only the basic technical support for core and special components, but also the reference of technical method for the similar mechanism design with complex structure and complex force.