Abstract: The invention concerns a method for preparing polyorganosiloxanes by hydrolysing organohalosilanes of formula (I) Ra R1b SiXc, in which R, R1 are identical or different radicals and represent hydrogen or linear or branched C1-C6 alkyls, aryls, alkylaryls or aralkyla X represents a halogen, and a+b+c=4 and 0<c<4; characterised in that it consists essentially in carrying out: at three successive hydrolysing steps (1), (2), (3), wherein the reaction medium is capable of exerting an increasing hydrolysing force on the organohalosilane (I), and optionally, at least a coalescing step (4); in that step (1) is a hydrolysis under pressure in the presence of an aqueous saturate hydrogen halide solution S1, at the reaction medium pressure and temperature; and in that the advanced hydrolysing step (31) brings into the reaction medium a water supply in the form of water free from or practically free from dissolved solutes and/or by means of aqueous hydrogen halide solution(s).