When a reliability analysis is performed according to the stress- strength interference theory,the fatiguestrength probability distribution needs to be obtained at an arbitrary fatigue life based on the existing fatigue experi-ment data of material.In this paper,a simulation method of fatigue strength probability distribution is proposedunder the condition that the fatigue life follows a lognormal distribution.In this method,a P- S- N curve at an arbi-trary survival probability with a finite life is reconstructed according to two known P- S- N curves,and then thefatigue strength probability distribution at an arbitrary fatigue life is inferred by means of the Monte Carlo simulationmethod.Finally,analyses on 20Cr2Ni4A are performed.It is found that the reconstructed P- S- N curve is highlyprecise,the fatigue strength probability distribution follows normal distribution and the simulation results accordwell with the equality principle and the fatigue strength degradation theory.The above results show that the pro-posed method is effective.