Abstract: The wedge-shaped space of the gradient magnetic field composed of neodymium-iron-boron was set up and experimental research on the natural convection heat transfer of oxygen gas in enclosure was presented based on magnetothermal convection induced by the gradient magnetic field.The laser speckle interferometry image for the natural convection of oxygen gas was obtained and the local Nusselt numbers as well as the temperature field could thus be derived.The results showed that the natural convection of oxygen gas was enhanced by using the gradient magnetic field in which magnetic acceleration is almost identical with gravitational acceleration in direction.