A novel radial magnetically insulated transmission line oscillator (MILO) has been proposed, based on a kind of conventional axial MILO. The radial MILO has very low impedance of about $2.5\Omega$, which permits much more electric power to be put in. It has a planar disk cathode with axial emission, which makes the repetition operation easy. The interaction between the wave and the electron beams is taking place in the radial direction, resulting in a more compact and light structure. The preliminary results of the particle in cell (PIC) simulation show that an L band radial MILO with two output ports can generate high power microwave with the total power of 6.3GW with a power efficiency of about 8% at 1.28GHz. This kind of radial MILO is hopeful to have more advantages and better performance than the conventional MILO.