PURPOSE: To obtain the titled spinning soln. capable of easily and continuously spinning a strand consisting of many gel fibers, silica fiber precursor, by using ethyl silicate and its polycondensate as starting material and by dissolving a fixed amount of polysiloxane synthesized in the presence of acid catalyst in alcohol.

CONSTITUTION: The polysiloxane (A) is synthesized by using ethyl silicate and its polycondensate (a) as starting material and by using acid catalyst (b) consisting of hydrochloric acid or nitric acid of 0.1W3.5wt.% acid concn. based on the amt. of the component (a). Then, the component (A) is dissolved in the alcohol (B) consisting of e.g. ≥90vol.% ethanol and ≤10vol.% methanol, so that the amt. of residue, SiO2, obtd. by heating the obtd. spinning soln. at 1,000°C is 42W48wt.%, to obtain the titled spinning soln. consisting of the alcohol soln. of polysiloxane. Then, the soln. is dry-spun to obtain silica fiber having the amt. of SiO2 above-mentioned when heated, ≤1wt.% moisture content at 50W100p (25°C) viscosity.