PURPOSE: A composition, prepared by incorporating an organosilicon compound containing functional groups with an inorganic filler, a curing catalyst and a diorganopolysiloxane containing functional groups, injection moldable at a low pressure without causing the curing inhibition, and suitable for molding a complicated molded article.

CONSTITUTION: (A) 100pts.wt. diorganopolysiloxane, expressed by the formula (R1 is alkenyl or mercaptoalkyl; R2 is alkyl, aryl, alkenyl or mercaptoalkyl; n is a positive integer 100W5,000), and containing 0.02W2mol% or alkenyl and/ or mercaptoalkyl groups is incorporated with (B) 0.1W20pts.wt. organosilicon compound having the same polymerization degree as that of the polysiloxane or below and 2mol% or more alkenyl and/or mercaptoalkyl groups in one molecule, (C) 5W100pts.wt. inorganic filler having a specific surface area ≥50m2/g and (D) 0.1W10pts.wt. curing catalyst. The resultant composition has a viscosity of 10W5,000 poises at 25°C, is stable at ordinary temperature and pressure for a long term without causing deterioration, curing, etc.