Abstract: A method for manufacturing of a silicone rubber base composition in a mass-like form, comprises:(A) preparing a freely flowable powdered silicone rubber composition comprising(a) a cross-linkable polydiorganosiloxane with a viscosity of at least 1.times.10.sup.5 mPa.s at 25.degree. C. and(b) an inorganic filler, and(B) continuously kneading and massing the powdered silicone rubber composition in a multiple-stage siding shear-type single-screw extruder.This method provides for continuous preparation of a silicone rubber base compound without the use of a dual-screw mixer-extruder having a large length to diameter ratio, without abrasive wear of screws and cylinders with such inorganic fillers as diatomaceous earth power, quartz or a similar large-grain and hard powders, without blackening of the mixed silicone rubber composition, and without production problems associated with the use of large quantities of fumed silica, sedimentary silica, or a similar reinforcing silica.