The invention provides a gas distribution and diffusion plate. The gas distribution and diffusion plate comprises a temperature control device which is used for controlling the temperature of the gas distribution and diffusion plate to keep stable. The gas distribution and diffusion plate has the advantages that the probability that reaction gas entering a reaction chamber is adsorbed on the surface of the gas distribution and diffusion plate and a recombination rate of reaction gas atomic activity radicals and the surface of the gas distribution and diffusion plate can be kept stable through the stable surface temperature, and accordingly the gas distribution and diffusion plate is capable of keeping gas molecules and the atomic radicals in the reaction gas participating in wafer processing stable basically, the stability of a wafer processing technology is guaranteed and the wafer processing quality and performance are improved; the risk that depositions of side reaction products on the surface of the gas distribution and diffusion plate form solid particles and fall to the surfaces of processed wafers in technology processing can be reduced through the stable surface temperature, so that the product yield is increased. The invention further provides a plasma processor.