In this project, magnetic field sensor has been presented using photonic crystal fiber PCF (type :Large-mode-area (LMA)) filled with Olive oil. Beside the Olive oil, Iron oxide (III) Fe2O3 magnetic nano-particles solution (concentration of 20 wt.% in H2O with average particle size < 30 nm) also filled in PCF and compared its sensitivity with that filled with Olive oil. The Olive oil Verdet constant was measured by using simple experiment for five laser wavelengths 405 nm, 532nm, 632.8 nm, 650nm, and 804.3 nm and the maximum measured value of Olive oil Verdet constant is 98.68 rad/T.m at 650nm laser wavelength. In order to enhance the magneto-optical properties of the Olive oil, Olive oil was uniformly doped with Fe2O3magnetic nano-particles provided by drying the Fe2O3Iron oxide (III) magnetic nano-particles solution. The magnetic solution shows lower Verdet constant than that of Olive oil at 650 nm but it has higher value of Verdet constant at 532 nm than that of Olive oil and Fe2O3magnetic nano-particles solution reachs 5.0042 rad/T.m for 0.56% concentration. Five PCFs length of 17 cm filled with different types of solutions and fluid had been prepared and tested using DC magnetic field and two laser wavelengths 532 nm and 650 nm. At 650 nm laser wavelength, the PCF filled with Olive oil shows the highest sensitivity among the others equal 3.509 rad /T and with maximum Verdet constant equal 12.37 rad/T.m .