To obtain a rubber composition useful for a tire having a tread excellent in strength and abrasion resistance by containing a blended substance of silica with a specific coupling agent and, if needed, a sulfur cured rubber reinforced with carbon black.

This silica-reinforced rubber composition comprises (A) 100 pts.wt. of at least one diene-based elastomer, (B) about 25-100 pts.wt. of a filler comprising precipitated silica and carbon black and (C) a silica coupler selected from among (i) a 3,3'-tetrathiodipropanol polysulfide mixture containing 1-8 S atoms in a polysulfide bridge or (ii) a mixture comprising about 95-25wt.% of the component (i) with about 5-75wt.% bis-(3-trialkoxysilylalkyl) polysulfide containing 2-8 S atoms in a polysulfide bridge. A weight ratio of the component C to the silica is about (0.01/1)-(0.2/1) and that of the silica to the carbon black is at least 0.1/1.