An organopolysiloxane emulsion composition having good age stability is prepared by (I) emulsifying a mixture comprising (A) an organopolysiloxane of formula: HO(R12SiO)nH, (B) a surfactant and (C-1) water to form a first emulsion composition and (II) effecting emulsion polymerization of the first emulsion composition in the presence of (D) an acid catalyst below 40° C. The target emulsion composition contains an organopolysiloxane product having a viscosity≧300,000 mPa·s at 25° C. and an octamethylcyclotetrasiloxane content≦3,000 ppm, and has an emulsified particle size≦500 nm.