Aircraft tow-tractor is one of the absolutely necessary ground support equipments (GSE) in the airport. The chassis is the framework on which the body and working parts of the tow-tractor, what plays a significant role in a entire vehicle design. The endurance and rigidity of the chassis have a direct influence on the reliability and practicability. In this paper, a simplified model is established for the carriage of aircraft towbarless tractor on the three-dimensional modeling platform--Proe5.0, and then mechanical finite element analysis are proceeding by Ansys12.0. The results show that the chassis model is of a appropriate structure and the design coincides with actual requirements, the Stress Concentration at the joint between carriage and wheel-grip mechanism has been reduced substantially. All trial results have laid a foundation for future design of the entire tractor.