<p>The elastic properties of cement-emulsified asphalt mortar (CAM) are governed by its complex microstructure; however, a clear quantitative relationship between the two remains limited. This work proposes a multiscale model to predict the macro elastic modulus of CAM from nano C–S–H gel. A cement hydration model is used to approximately characterize the microstructure of CAM. Homogenization methods including the Mori–Tanaka, Self-Consistent, and Generalized Self-Consistent methods are employed for upscaling calculation. The evolution law of aspect ratios of asphalt and calcium hydroxide crystals (CH) on asphalt–cement ratio (A/C) is obtained through reverse analysis according to the multiscale model. The multiscale model is validated by comparing with extensive experimental data. The effects of sand particle size, interphase thickness, A/C ratio, water–cement (W/C) ratio and sand–cement (S/C) ratio on the elastic behavior of CAM are studied. Results show that the elastic modulus of CAM is inversely proportional to interphase thickness, W/C, and A/C ratios, but positively correlated with S/C ratio.</p>