This invention concerns a sampling procedure for an aqueous hydrosoluble polymer solution flowing in a main circuit, enabling a sample to be collected to undergo at least one analysis under ambient air giving at least one property of the hydrosoluble polymer characterised in that a stabilizing solution is added to the aqueous hydrosoluble polymer solution, according to a discontinuous addition method, before or after sampling from the main circuit, so as to obtain a sample comprising a mixture of aqueous hydrosoluble polymer solution and stabilizing solution in which the hydrosoluble polymer is protected against attacks it may undergo in an atmosphere containing at least 10% by volume of oxygen.