In this paper, magnetic nanocomposites were synthesized by embedding ferric oxide nanoparticles into carboxymethyl cellulose (CMC) using co-precipitation method. The properties of the synthesized nanocomposites in the presence of magnetic field were compared to the synthesized nanocomposite in normal condition. The magnetic properties of the nanocomposites were studied by a vibrational sampling magnetometer (VSM) to investigate the effect of the magnetic field on the magnetic properties. The results showed that the presence of magnetic field during the synthesizing, increased the saturation magnetization about 51%. X-ray diffraction (XRD) analysis confirmed the crystallinity of all samples. The SEM images revealed the nanoparticles homogenous dispersing in the composites. Infrared Fourier spectroscopy (FTIR) results confirmed the formation of iron oxide bonds in all samples. The increase of saturation magnetization can be attributed to the magnetic moment alignments by the magnetic field. Magnetic nanocomposites with higher magnetic properties can further develop their application.