The present invention is to provide a diene rubber composition and a cross-linked diene rubber thereof excellent in tensile strength, wear resistance and processability, keeping compatibility of both good fuel efficiency and high gripping property, and a production method thereof. What is characterized in the composition is that the composition is comprised of 100 parts by weight of a diene rubber having a molecular weight distribution expressed in terms of the ratio of the weight-average molecular weight to the number-average molecular weight of 1.1 to 30, 20 to 200 parts by weight of silica and a cationic polymer, and that a toluene-insoluble rubber content per gram of the silica within the range from 0.2 to 1 g, and diene cross-linked rubber thereof. What is characterized in the production method is that the method comprises steps of allowing rubber latex stabilized by an anionic emulsifying agent to react with an aqueous suspension of silica containing a cationic polymer and effecting co-coagulation of rubber in the rubber latex with the silica in the aqueous suspension within a specific pH range.