Study on fatigue strength evaluation system for automoblie components, particularly for tie rod and rack bar which are the components of streering system, was made. Stress status of critical point was found by using finite element method. And fatigue property of components was obtained from the results of raw material fatigue test through considering modifying factors which quantifies the effects of various parameters such as size, loading type, roughness, surface treatment, notch effect. Fatigue analysis for prooving ground load histories was perfomed not only using multiaxial damage rules with the results of finite element method but also using ordinary fatigue analysis method for notched members. Finally, with the results obtained through the analysis and using expert system, fatigue analysis expert system for tie rod and rack bar was implemented.