Structure parameters of minerals in human bone, bioapatite, are very important for biomaterials. In situ micro-XRD and Rietveld structure refinement were used to extract subtle structure information of human ribs. Rietveld refinement testified that lattice parameters, crystallite size and microstrain for cortical and cancellous bones were significant difference. Anisotropic crystallite sizes of human rib showed preferential growth of apatite along c-axis and the graded variation at radial direction of bone axis. The variations of the subtle structures of bioapatite, such as, P occupancy and P-O2 bond length, as well as distortion index of P-O tetrahedron, demonstrated the tendency of mineralization and the content of CO3 2- in human ribs.