Abstract: During the operation of a vehicle, a torsion shaft in the gearbox broke down several times, cracks are sprout and extended from the root of the spline transition curve. Through analysis, it is found that the shaft was shocked with a large impact load during serviee, which led to the spline transition part of the transmission shaft plastic deformation and strain damage. According to Manson formula, combined with the finite element plastic deformation analysis of the shaft, the low cycle fatigue life calculation based on strain damage was carried out, and the low cycle fatigue life was obtained to be 2 574 times, which was very close to the result of bench test. The study provided a feasible exploration for the low cycle fatigue failure analysis of the drive shaft under large impact shocks.