An antifouling condensation curing organopolysiloxane composition is prepared by premixing a part or all of (A) a diorganopolysiloxane free of a reactive group with a part or all of (B) silica to form a premix, then mixing the premix with the remainder of (A) and (B), (C) a base diorganopolysiloxane, and (D) a silane. The composition has a good balance of low viscosity and high thixotropy, can be thickly coated in a single pass, and cures into a coating having rubber strength and surface smoothness and exhibiting satisfactory antifouling property over a long period of time.