Nanoparticles have become a promising material for water treatment and the production of more active adsorbents that combine carbon-based adsorbent and magnetite properties. The water extract from Calotropis procera leaves is used as a capping and reducing factor to optimize nanoparticle production and stabilize the produced magnetite nanoparticles. For this reason, the preparation and characters of magnetite nanoparticles were studied. The prepared nanoparticles were described by XRD, FTIR spectroscopy, imaging by SEM and TEM, EDX analysis, surface area, and pHpzc. The FTIR result illustrates the existence of magnetite and goethite, OH and COOH groups worked as an agent for reduction and capping for Fe3O4 inside nanoparticles. The results were confirmed by XRD examination, which illustrates the inverse spinal shape with a lattice structure that is face-centered cubic of magnetite and orthorhombic structure of goethite and the calculated crystalline index CI = 37.78%. The EDX analysis of nanoparticles showed O (23.53%) and Fe (66.94%). The particle size ranges from 10 to 50 nm where sizes ranged from 5-25 nm was represented 70% and the calculated average diameter of nanoparticles is 30 nm, with pHpzc is 8.58, and the surface area is 93.338 m2/g. The results were successful to produce nanoparticles of magnetite prepared by eco-friendly biosynthesis method using Calotropis procera leaves extract.