Zn-doped hydroxyapatite/graphene (Zn-doped HA/GP) composite was successfully in situ synthesized by one-pot hydrothermal treatment for the first time, and was studied through experimental analysis and density functional theory calculations. The effects of a series of Zn contents (0mol%, 1mol%, 5mol%, 10mol % and 20mol%) on the HA crystal structure, the morphology and composition of composites were also investigated. The obtained doped composites were analyzed and characterized by the techniques of field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray detector (EDX), Xray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and Raman spectroscopy. Density functional theory calculations of Zn-doped HA showed that the replacement of Zn ions in HA crystal lattice could cause the OH- group to move off the c axis toward the Zn ions and become closer to the PO43- group, resulting in the formation of hydrogen-bond between OH and PO43- groups. The morphology of Zn-doped HA/GP composite showed that Zn-doped HA grains with molar fraction of 1 mol% Zn are intimately attached on the surface of graphene whereas the amounts of Zn-doped HA attached on the GP surface reduce obviously and the interfacial interactions are weakened accordingly as the Zn doping amount increased from 5 to 20 mol%, which indicates that the low crystallinity of Zn-doped HA particles due to an increasing Zn content may have a negative effect on interfacial interaction between Zn-doped HA and GP. (C) 2017 Elsevier B.V. All rights reserved.