Magnetic nano capture agent (MNCA)-based magnetic separation can remove heavy metals from blood efficiently and safely. It has been considered as the next-generation therapy for heavy metal intoxication. In this work, we report the first use of MNCA to remove arsenic (As) with high efficiency from blood. MNCA with a flexible, non-covalent and biocompatible surface layer has been synthesized by packaging cetyltrimethylammonium bromide (CTAB) and bovine serum albumin (BSA) together with oleic acid coated magnetic iron oxide nanoparticles (MNP@OA) via Van der Waals force. This surface layer enhances arsenic anion diffusion from the surface to the binding sites, leading to increased arsenic removal performance of MNCA. The adsorption capacities of BSA and CTAB enfolded MNP@OA (MNP@CTAB-BSA) for As (III) and As (V) are 131.00 mg g−1 and 119.58 mg g−1, respectively. 89.02% of As (III) and 81.78% of As (V) are removed from blood using MNP@CTAB-BSA, and the residual concentrations of As (III) and As (V) in blood decrease from 400.00 μg L−1 to 43.93 μg L−1 and 72.88 μg L−1, respectively. The as-synthesized MNP@CTAB-BSA shows excellent biocompatibility. Under operation condition, only 0.80% of hemolysis and 1.64% of plasma protein adsorption are induced by MNP@CTAB-BSA, and the cell viability of peripheral blood mononuclear cells (PBMCs) is more than 95.53%. This study paves a fast, safe and effective way for arsenic intoxication therapy.