We investigate the radiation damping experienced by a dielectric spherical particle when it is illuminated by an electromagnetic plane wave within the Rayleigh regime. We derive the equivalent electric dipole of the moving particle and subsequently calculate the electromagnetic force acting on it from two different approaches. In the first approach, we calculate the force from the integration of stress tensor and field momentum. In the second one, we calculate the force directly from the integration of the force density. Our derivations reveal that the damping coefficient is equal to $6P_{scat}/mc^2$ along the propagation direction, whereas it is $P_{scat}/mc^2$ along perpendicular directions. Here, $P_{scat}$ denotes the power scattered by the particle, and $mc^2$ represents the particle's mass energy. The radiation damping derived in this study sets upper limits on the quality factor of optically levitated objects and ensures the existence of a steady-state solution of the particle's dynamics.
