X-ray phase-contrast imaging (XPCI) can dramatically improve soft tissue contrast in X-ray medical imaging. Despite worldwide efforts to develop novel XPCI systems, we do not yet have a numerical framework to rigorously predict the performance of a clinical XPCI system at a human scale. In this study, we propose to develop such a simulation framework to accomplish this using the breakthroughs in two main components: a realistic human-scaled numerical phantom for XPCI, and a wave optics-based simulator for accurately propagating X-ray wave through a realistic human numerical phantom. For the numerical phantom, the biggest challenges are to incorporate various organs with multi- scale structures in a human-size phantom and to define material properties for human body parts under normal and a variety of pathophysiological conditions. To address these issues, we will extend the XCAT phantom, a human phantom that is widely used in medical imaging simulation, to incorporate sub-organ structures and tissue textures, and to assign appropriate material properties to various tissues for XPCI simulation. For the simulator, we have recently demonstrated the possibility of XPCI simulation at a human scale by applying a wave optics-based imaging model to XCAT phantom. In the proposed project, we will develop a general-purpose XPCI simulator that can be used with variety of geometries, X-ray optics, and tissue models. Using the data we have already acquired on a synchrotron-based, high-performance XPCI setup, we will validate the simulator so that its predictions match experimentally acquired data. Finally, we will distribute the program with a graphical user interface in order that the users can easily simulate their own XPCI systems. Source codes and a detailed user manual will be distributed as well.