The invention discloses a light condensing type photovoltaic and photothermal device based on magnetic nano fluid. The light condensing type photovoltaic and photothermal device comprises a photovoltaic and photothermal integrated device, Fresnel condensers, a flow control valve, a first water pump, a second water pump, a magnetic nano fluid heat insulation water tank, a heat exchanger, a vertical fixing support, a horizontal fixing support, a hot water heat insulation water tank and a throttling valve. By means of the light condensing type photovoltaic and photothermal device, the Fresnel condensers are used for condensing solar radiation to a solar photovoltaic and photothermal CPV/T device, and the photoelectric and photothermal conversion efficiency is improved; and in addition, output of energy of a system is adjusted and controlled by adjusting and controlling the size of a magnetic field, and the utilization rate of solar energy is increased. Meanwhile, due to the frequency-division absorbing feature and the efficient heat conduction feature of the magnetic nano fluid, the heat energy of a PV module can be sufficiently and fast absorbed, the temperature of the PV module is fast reduced, and the high photoelectric and photothermal conversion efficiency is maintained.