The damage of large-aperture optical components caused by organic contamination limits the performance improvement of high-power laser facilities. We propose an in situ plasma cleaning technology to remove the organic contaminants on large-aperture optical components, demonstrated by the simulated equipment. The cleaning characteristics of the equipment were investigated by spectral diagnosis. The cleaning capability coefficient was defined to evaluate the performance of the plasma equipment. Then diffusion properties of reactive species along the surface of optical components were elucidated under various charge parameters, including powers, source frequencies, and gas pressures. We discuss the underlying cleaning mechanism for removing organic contaminants. A new plasma cleaning model is established to predict the treatment time with the cleaning capability coefficient.