We report the stabilization of ferrofluid in oleic acid synthesized by ultrasonication of nanosized Fe3O4 particle and grafts of poly-dimethylsiloxane (PDMS) with acrylic acid and methacrylic acid. The nanosized polymers were prepared by microwave-assisted copolymerizaion of PDMS chain with 0.029mol of acrylic acid and 0.023mol of methacrylic acid. The stability of the prepared materials was characterized by Fourier Transform Infrared (FTIR) spectroscopy, thermal analysis (TG-DTA-DTA), H-1 NMR and transmission electron microscope (TEM). The result indicate that the ferrofluid have nanometric size with high thermal stability. A comparison of both the nanomagnetic fluids has been discussed. The structure of the fluids has been proposed on the basis of the experimental results.