A pneumatic radial tire comprises a tread portion having a two-layer structure of a cap rubber layer disposed outward in the radial direction and a base rubber layer disposed inward in the radial direction, in which an outer surface of said base rubber layer in the radial direction being existent in a position corresponding to not less than 20% of a depth of a main groove formed in the tread portion outward from a bottom of the main groove in the radial direction, and the base rubber layer being compounded with a recrosslinking inhibition assistant and/or an inorganic compound powder.