Based on the seven conventional aero-metals fatigue test data, the relationship between cyclic stress-fatigue life and the S-N curve are obtained by the Least Squares Support Vector Machine(LSSVM) firstly. The S-N curves got by LSSVM and by the power function and the three-parameter equation are compared. It is found that the LSSVM not only can be used to describing the relationship between the cyclic stress-fatigue life, but also is the best method compared with the power function and the three-parameter equation. Using the S-N curve got by LSSVM, the fatigue life under the cyclic stress can be precisely obtained, and the fatigue limit can be obtained too. So, the security can be ensured for the structure design and using.