PURPOSE: To provided a reinforced rubber composition capable of giving a vulcanized product having excellent tensile modulus, tensile strength and elongation, and high moldability, and composed of a continuous rubber phase and a dispersed phase of thermoplastic resin fine particles wherein both phases are bonded together through a chemical bond via a novolac-type phenolic resin.

CONSTITUTION: The objective composition is composed of a vulcanizable non- crosslinked rubber as the continuous phase and fine particles of thermoplastic polymer having -CONH- group in the polymer molecule as the dispersed phase, wherein said continuous phase and said dispersed phase are bonded together through a chemical bond via a novolac phenolic resin. The rubber is preferably NR of SMR-L wherein the plasticity retaining index of the natural rubber is ≥80. The fine particle of the thermoplastic polymer is preferably nylon, etc. having a melting point of 200W220°C and particle diameter of 0.1W0.5μ, and ≥50wt% of the particle has essentially spherical form. The phenolic resin is a precondensate of a novolak-type phenol formaldehyde resin.