Abstract: P-S-N curve is a basis of reliability design and analysis. It will require a lot of time and samples to determine a group of P-S-N curve. So how to design the test program becomes a practical problem. Using Monte Carlo method, this paper simulated fatigue test for determining P-S-N curve and the number of stress levels as well as the sample number under each stress level. Therefore the optimum test program is given. The conclusion is that compared with commonly used four-stress level or five-stress level tests the proper three-stress level or four-high-stress level test can greatly reduce test time as well as samples, and at the same time reach the same accuracy when determining P-S-N curve.