The invention provides organopolysiloxane compositions for a releasable substrate which are superior in curability, anti-static property, oil resistance, and slipperiness, and provide a good releasability to the treated objects, said composition comprising (1) 100 parts by weight of an organopolysiloxane which comprises at least two alkenyl groups and 5 to 50 mol % of a chemical unit expressed by formula (I) ##STR1## (2) 1 to 100 parts by weight of an organohydrogen polysiloxane which comprises at least three hydrogen atoms bonded to silicon atoms per molecule, and (3) a catalytic amount of platinum or platinum compound.