Light scattering from a ferrofluid in a magnetic field stems from the anisotropic chain structure formed in the ferrofluid, In this article a theoretical model of light scattering from a ferrofluid in a magnetic field is established on the basis of classical dipole element oscillation theory, while the scattering effects caused by the anisotropic chains play the most important roles in scattering the incident light in space. The theoretical formula shows that the distribution of light intensity in space is a continuous banding symmetric about the incident center which has been confirmed by our experimental results. From the formula, it also can be concluded that the width distribution of the chain has an important influence on the distribution of light intensity in space. The wider the width distribution, the weaker is the light scattering; only when the expectation value of the width distribution approaches the wavelength of the incident light does the light scattering from the ferrofluid become obvious, The intensity of the scattered light is proportional to the square of the volume of the chain, This result is in accordance with classical scattering theory. An experimental setup has been built to measure the distribution of light intensity in space.