A high strength glass fiber is prepared by following steps: weighing raw materials according to a mass percentage of 50-60% silica sol, 24-31% aluminum sol, 8-11% magnesia, 4-5% calcium oxide, 0.1-2% titanium dioxide, 0-0.5% ferric oxide, 0.5-2% niobium pentoxide, 0.5-1.5% antimony trioxide, 0.3-1.5% bismuth nitrate, and 0.1-0.5% boric acid. Deionized water is added. The raw material undergoes mixing by ball milling, spray-drying, calcining, isostatic pressing, melting, and wire-drawing. The invention adopts silicon sol, aluminum sol and bismuth nitrate. Through ball milling and spray-drying, silicon aluminum barium plasmas is evenly coated on surface of other oxide powders. Then nano particles, of silica, alumina and bismuth oxide are obtained by calcining. Under the effect of the high specific surface energy of nano particles, and the close contact of each component, high strength glass fiber is obtained in relatively low fiber drawing temperature while the glass melting temperature and time are significantly reduced.

It has been found that conventional cheap waterglass qualities in a strongly acidic medium react to give high-purity silica grades, the treatment of which with a base leads to products which can be processed further to give glass bodies with low silanol group contents.