<p>The increasing demand–supply disparity of natural sand has induced the widespread adoption of manufactured sand in various projects. The particular stone powder in manufactured sand has a notable impact on the hydration process of cementitious materials, which causes variations in the internal moisture content of the manufactured sand concrete (MSC). One of the key components of many degradation processes, such as shrinkage and cracking, is the amount of water content in the MSC pores. Establishing a dynamic moisture distribution model for MSC with regard to hydration level is the aim of this work. The modeling method accounts for variations in humidity brought on by moisture diffusion as well as cement hydration. The dynamic humidity distribution of MSC during the separate impacts of self-desiccation and water diffusion was discussed along with parameters of the moisture model, i.e., hydration degree (<i>α</i>), hydration-induced humidity reduction value (<i>H</i>_s), and moisture transfer coefficient (<i>D</i>). Subsequently, the HETVAL (a user subroutine for defining heat generation and transfer) and USDFLD (a user-defined field variable subroutine for material property modification) were compiled on the ABAQUS secondary development platform to simulate the dynamic moisture distribution within MSC, based on the parameters of the moisture model. The fitting results of the model agreed well with the results from experiments. The proposed model can be subsequently utilized to analyze shrinkage-induced stress fields, as well as to control cracking in MSC structures.</p>