A method for producing a modified solution polymerized diene rubber, comprising: i) initiating polymerization of a conjugated diene compound and an aromatic vinyl compound in a hydrocarbon by an organolithium compound or in the co-presence of a secondary amine compound; ii) after completion of the polymerization, adding a tin compound of formula to treat the diene rubber so that the content of three or more branched component is 5 to 30%; iii) adding the silane compound of formula, whereby the content of two-branched component of the diene rubber is 30% or less; and iv) steam coagulating and drying the obtained polymer composition, so that the content of two or more branched component increases by 10 to 50% with respect to the state before steam coagulation, and wherein the modified solution polymerized diene rubber is thermally stabilized to the extent that the Mooney viscosity (a) of the rubber measured after said steam coagulation and drying, varies by not more than 10 from the Mooney viscosity (b) of the rubber measured when it is further heat-treated for 20 minutes with a subsequent 130 °C roll mill. [Formula 1] (R 1) n -Sn- 4-n Formula wherein R 1 is an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 1 is1 to 12 carbon atoms, X is a halogen compound of iodine, bromine or chlorine, n is an integer of 0 or 1, [Formula 2] (R 2 0) m -Si-(R 3) 4-m Formula wherein R 2 is an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 2 is 1 to 12, or an alkyl group, an aromatic group or an allyl group containing a nitrogen atom in these functional groups, R 3 is a an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 3 is 1-12, or an alkyl group, an aromatic group or an allyl group, containing an oxygen atom and/or a nitrogen atom in these functional groups, m is an integer of 2 to 4. i) initiating polymerization of a conjugated diene compound and an aromatic vinyl compound in a hydrocarbon by an organolithium compound or in the co-presence of a secondary amine compound; ii) after completion of the polymerization, adding a tin compound of formula to treat the diene rubber so that the content of three or more branched component is 5 to 30%; iii) adding the silane compound of formula, whereby the content of two-branched component of the diene rubber is 30% or less; and iv) steam coagulating and drying the obtained polymer composition, so that the content of two or more branched component increases by 10 to 50% with respect to the state before steam coagulation, and wherein the modified solution polymerized diene rubber is thermally stabilized to the extent that the Mooney viscosity (a) of the rubber measured after said steam coagulation and drying, varies by not more than 10 from the Mooney viscosity (b) of the rubber measured when it is further heat-treated for 20 minutes with a subsequent 130 °C roll mill. [Formula 1] (R 1) n -Sn- 4-n Formula wherein R 1 is an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 1 is1 to 12 carbon atoms, X is a halogen compound of iodine, bromine or chlorine, n is an integer of 0 or 1, [Formula 2] (R 2 0) m -Si-(R 3) 4-m Formula wherein R 2 is an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 2 is 1 to 12, or an alkyl group, an aromatic group or an allyl group containing a nitrogen atom in these functional groups, R 3 is a an alkyl group, an allyl group or an aromatic group, wherein a carbon number of R 3 is 1-12, or an alkyl group, an aromatic group or an allyl group, containing an oxygen atom and/or a nitrogen atom in these functional groups, m is an integer of 2 to 4.