This paper proposes a new model to estimate life of structures for combined damage of high and low cycle fatigue. The model mainly consists of a new damage indicator and strain-life fatigue curve. The model predictions are verified by comparing with fatigue test results of some materials. The proposed model is applied to estimate the fatigue life of a bridge member for combined damage of high cycle and low cycle fatigue caused by usual traffic and earthquake loadings. Finally, the importance and applicability of the proposed model is confirmed. Key words: High cycle fatigue, low cycle fatigue, combined damage, railway, bridge.