Abstarct: In this thesis numerical and experimental study of low-cycle fatigue life of steel SS304 loading was investigated. First, in order to better understand the behavior of elastic-plastic behavior of steel SS304 in uniaxial tensile test was modeled. After that, the experimental analysis to estimate life of this steel according to the energy approach and image processing techniques have been investigated. At the end, the fatigue life estimation of numerical analysis with comsol software discussed. The results obtained from the mathematical modeling of the tensile test corresponded well with the behavior of SS304 steel. Approach in order to experimental analysis considering hysteresis energy released during the loading cycle, the various definitions of energy is expressed, energy released in the first cycle, the last cycle, the percentage of the cycle, the total energy cycles over and consider all possible states baxsed on the least cycles are done. Experimental results show that, in general considering the the intermediate cycles are far more accurate than other modes of energy. In the image processing, when the sample is under cyclic loading, the surface is photographed using a microscope camera. Image processing results obtained from the analysis of these images shows that fatigue is related with the appearance of the sample, near the end of the cycle, the graph obtained from the image processing will continue to deteriorate. After reviewing software for numerical analysis to estimate fatigue life fatigue analysis capabilities have finally been chosen Comsol software and modeling was conducted. The results obtained showed that numerical simulation software, baxsed on the criteria of fatigue, stress and strain, the detection of fatigue life is concerned, however, are closer to the experimental results, it can not accurately estimate the lifetime of the material.