The steering mechanism is the core components of the power-shift steering transmission(PSST),where the failure will result in insufficient steering power and loss of steering ability of vehicles.For the reliability of the steering mechanism,not only the faults are summarized and diagnosed,but also the failure modes,effects and hazards are investigated in detail,the maximum probability of failure influence reaches 0.9.Moreover,the reliability of the steering mechanism is improved by optimizing the struc-ture and assembly process,which is verified by the reliability test of the steering mechanism.Therefore,the improved technical measures are effective and the optimized steering mechanism has met the reliability requirements of PSST.