The purpose is to study the linear birefringence and dichroism properties of the kerosene-based Fe3O4 magnetic fluid under the magnetic field, which have been theoretically analyzed and simulated numerically based on the dipole oscillation model. The experimental platform is designed to test the optical properties of kerosene-based Fe3O4 magnetic liquid in different volume densities under the magnetic field. The theory and numerical simulation show that the birefringence and dichroism of different polarized light have different variation trend under the magnetic field: the birefringence and dichroism of parallel polarized light decrease, but the ones of perpendicular polarized light increase; those are in proportion to the volume density; the transmittance in the interface between glass and ferrofluids is almost unchangeable. The experimental result is in agreement with the numerical simulation that provides the theoretical and experimental basis for designing the light switch and the application in measurement of the magnetic field and current sensors.