Previous research shows that the water-to-cement ratio of parent concrete and residual mortar content has a significant effect on the strain at the peak stress of recycled aggregate concrete（parent concrete）. However， the available models do not account for this effect. Therefore， 4 different peak strain models based on the composite material theory was derived， which could account for the influence induced by water-to-cement ratio and residual mortar content. All of them have been validated against the collected 100 groups of test results. The results show that the predictions for these models differ considerably. Hirsch's model and Counto's model have relatively high accuracy. The mean value and coefficient of variation for the ratios of predictions to test results are 0.978-1.000 and 0.072-0.080， respectively.