Predicting fatigue damage for structures which are subjected to variable loading conditions is a complex issue. A fatigue failure is particularly insidious because it happens without any visible warning in progress, so it is important to estimate the fatigue life of a component that subjected to cyclic loading. In this research work, the stress-life method is used to investigate the effect of loading frequency on fatigue life of Green onyx under completely reversed loading by using a developed apparatus, based on rotating beam fatigue testing machine (R.R.Moore) that commonly used for laboratory fatigue test in metals. Result manifested that the fatigue life of green onyx samples depend on the frequency level and the fatigue life improved with an increase in loading frequency level. Also the effect of loading frequency on fatigue limit of samples was investigated. Results showed that the fatigue limit independent from the frequency level. Applicability of cumulative damage curve, linear and double linear approach was investigated for rock samples and the new model proposed in each damage theory to predict the fatigue life of green onyx samples. Then the accuracy of this proposed equation examined by the large number of experimental data which obtained from H-L loading tests.