The present invention relates to a method for preparing an aluminosilicate polymer and the polymer resulting from this method. Said method consists in treating an aluminum halide with an alkyl orthosilicate only having hydrolyzable functions with an aqueous alkali, in the presence of silanol groups, aluminum concentration being maintained at less than 0.3 mol/l, the Al/Si molar ratio being maintained between 1 and 3.6 and the alkali/Al molar ratio being maintained between 2.3 and 3; and then in stirring the resulting mixture at ambient temperature in the presence of silanol groups for long enough to form the aluminosilicate polymer.