To obtain an organosilicon polymer composition having excellent storage stability and showing good workability in mixing with e.g. an inorganic filler without dissolving it in an organic solvent by mixing a specified silicon- containing polymer with a specified low-molecular liquid compound.

This composition contains 15-90 pts.wt. silicon-containing polymer (a) containing at least one R1O group [wherein R1 is hydrogen or a l-5C (un)substituted alkyl, provided that R1s may be the same or different from each other when a plurality of R1s are present in the molecule] and at least one polysiloxane group at least one of the Si atoms of which is bonded to R1O to form an Si-O-C bond in the molecule and being soluble in the following compound (b) and 10-85 pts.wt. (the total is 100 pts.wt.) normally liquid compound (b) having a solubility parameter(SP) of 8 or above and a molecular weight of 190 or above.