According to the physical structure model of cement asphalt(CA) binders with low asphalt cement ratio, in reference to the related theories of cement based materials and two phase composites, 4 mathematical models to characterize the relationship between compressive strength and composition parameters of CA binders were developed. The compressive strength, porosity and volume fraction of asphalt for CA binders with different mix proportions were investigated. Results show that the volume fraction of asphalt is the essential factor which affects the compressive strength, while the influence of porosity on compressive strength is slight. The modified Schiller model is most suitable to characterize the compressive strength of CA binders, the calculated results fit well with the experimental results. On the basis of the quantitative relationship between each phase volume fraction and mix proportion parameters of CA binders, the mathematical relation between the compressive strength of CA binders and the mix proportion parameters with regard to asphalt cement ratio, water cement ratio and cement hydration degree is clarified.