A method for preparing an organopolysiloxane emulsion composition comprising the steps of: (I) emulsifying a mixture to form a first emulsion composition, the mixture comprising (A) 100 parts by weight of organopolysiloxane having the general formula : HO(R 1 2 SiO) n H wherein each R 1 independently is hydrogen or substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms and n is such a number that the organopolysiloxane has a kinematic viscosity, as measured by an Ostwald viscometer, of from 200 mm 2 /s to less than 2,000 mm 2 /s at 25°C, said organopolysiloxane having an octamethylcyclotetrasiloxane content not more than 1,000 ppm, (B) 1 to 8 parts by weight of surfactant, and (C-1) 1 to 10 parts by weight of water per 100 parts by weight of component (A), and wherein the first emulsion composition is prepared using an emulsifying machine for processing emulsified particles under shear force to a smaller size, and (II) optionally adding (C-2) 0 to 10,000 parts by weight of water and effecting emulsion polymerization of the first emulsion composition in the presence of (D) an acid catalyst, which is optional when component (B) is catalytic, at a temperature lower than 25°C, thereby forming a target organopolysiloxane emulsion composition which contains an organopolysiloxane product having a viscosity, as measured using a rotational viscometer, of at least 300,000 mPa·s at 25°C and an octamethylcyclotetrasiloxane content of up to 3,000 ppm, and has an emulsified particle size of not more than 500 nm, wherein said particle size is a median diameter, as measured by a laser diffraction/scattering mode particle size distribution analyzer, and wherein the octamethylcyclotetrasiloxane content is measured by the method disclosed in the description. (I) emulsifying a mixture to form a first emulsion composition, the mixture comprising (A) 100 parts by weight of organopolysiloxane having the general formula : HO(R 1 2 SiO) n H wherein each R 1 independently is hydrogen or substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms and n is such a number that the organopolysiloxane has a kinematic viscosity, as measured by an Ostwald viscometer, of from 200 mm 2 /s to less than 2,000 mm 2 /s at 25°C, said organopolysiloxane having an octamethylcyclotetrasiloxane content not more than 1,000 ppm, (B) 1 to 8 parts by weight of surfactant, and (C-1) 1 to 10 parts by weight of water per 100 parts by weight of component (A), and wherein the first emulsion composition is prepared using an emulsifying machine for processing emulsified particles under shear force to a smaller size, and (II) optionally adding (C-2) 0 to 10,000 parts by weight of water and effecting emulsion polymerization of the first emulsion composition in the presence of (D) an acid catalyst, which is optional when component (B) is catalytic, at a temperature lower than 25°C, thereby forming a target organopolysiloxane emulsion composition which contains an organopolysiloxane product having a viscosity, as measured using a rotational viscometer, of at least 300,000 mPa·s at 25°C and an octamethylcyclotetrasiloxane content of up to 3,000 ppm, and has an emulsified particle size of not more than 500 nm, wherein said particle size is a median diameter, as measured by a laser diffraction/scattering mode particle size distribution analyzer, and wherein the octamethylcyclotetrasiloxane content is measured by the method disclosed in the description. <EOS>