The purpose of inflammation is to protect the host against microbes, to repair injuries, and to contribute to the removal of apoptotic cells or immune complexes, when it becomes excessive and chronic, this process can contribute to several pathologies including the development of cancer.The study of complement system describes the role of complement proteins in the regulation and synchronization of an acute inflammatory reaction, which aims to eliminate pathogens and clear damaged cells and proceeds with obvious benefit for the host, And also the contribution of complement to the pathophysiology of selected diseases. To illuminate the nature of complement receptors C5aR and C3aR, and the nature of their binding correspondingly, need the building of homology models and a stepwise structure refinement of the built models through molecular dynamics simulations. In this book, we focus on the homology modeling of Complement receptors to provide vast structural features. Moreover, validation of the developed models through available mutation data. Application of docking methods against these models is necessary for virtual screening to detect novel ligands.