Chassis is one of the key components of tracked test vehicle. The strength and rigidity of chassis must be considered and structure resonance should be avoided during the process of structure design. The stress nephogram and strain nephogram of chassis are obtained, after static analysis in the finite element analysis software ANSYS. The maximum stress is 65.13MPa and the maximum strain is 0.00032mm. They both occur in the place where stiffener of bottom plate and side plate of speed reducer box are welded together. A kind of improved scheme is put forward, considering that the welding allowable stress is smaller than the allowable stress of parent material, and also the stress concentration and residual welding stress exist, though the maximum stress is in the allowed range. Static analysis is made to the improved chassis. The maximum stress becomes 45. 573MPa with 30% reduced, and the maximum strain becomes 0.00022786mm with 28.8% reduced. And the position of maximum stress and maximum strain transfer to the internal corner of crossbeam. And the first six extended natural frequencies of the improved chassis are obtained via modal analysis.