The presence of chromium ion in drinking water was found to be toxic and carcinogenic nature. Hence an attempt has been made for the synthesis of magnetic (Fe3O4) fabricated with nano-hydroxyapatite (n-HAp)/gelatin (Gel) biocomposite by both in-situ precipitation (In-situ) and hydrothermal (Hydro) methods. The hydrothermal assisted Fe3O4@n-HApGel biocomposite have achieved an enhanced sorption capacity (SC) than in-situ precipitation method. The physicochemical properties of the synthesized adsorbents was widely characterized using various advanced instrumental technique likes FTIR, XRD, SEM, EDAX, TEM and BET surface area analysis. Chromium adsorption mechanism of hydrothermal assisted Fe3O4@n-HApGel composite is decided by electrostatic attraction with surface complexation and reduction. The chromium adsorption behaviour of hydrothermal assisted Fe3O4@n-HApGel biocomposite was interpreted by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The thermodynamic experimental data of Fe3O4@n-HApGel biocomposite refers that the chromium sorption process is an endothermic and spontaneous nature. For the reusability of Fe3O4@n-HApGel composite, that can be easily recycled more than 5 cycles using NaOH eluent. In addition, the magnetic biocomposite is also suitable for treating chromium polluted ground water.