A hydrolyzable group-containing organohydrogenpolysiloxane is prepared by (A) reacting (a) an organosiloxane with (b) an organosilane or organosiloxane containing a hydrolyzable group, at least one of components (a) and (b) containing hydrosilyl, in the presence of a superstrong acid catalyst, (B) adding an inorganic basic neutralizing agent and/or an adsorbent to the resulting reaction solution, and (C) removing the neutralized and/or adsorbed form of the superstrong acid catalyst. The process proceeds in an essentially non-aqueous system, and the organohydrogenpolysiloxane free of residual acidic catalyst is obtainable at low cost.