Abstract: The equivalent number of strain cycles plays an important role in seismic response analyses. The existing calculation methods for the equivalent number of strain cycles are mostly based on accumulated damage theories. However, the time history of an earthquake load is required in the prediction using these methods, which is complicated in the equivalent conversion. In order to address these issues, 296 records of horizontal seismic time-history records, which cover different kinds of the epicenter distance and magnitude, are used in this study. The equivalent number of strain cycles is calculated for the sand with a relative density of 45% subjected to the selected earthquake load. Based on the statistical analysis using the nonlinear mixed-effects model, a predictive model for the equivalent number of strain cycles is proposed for both unidirectional and bi-directional earthquake loads. By examining the p-value and the residual distribution, the results show that the predictive values are reasonable. The proposed predictive model is validated by the measured data.