The object of the invention is the stabilising composition for stabilising clay-loam soils in the form of a liquid solution, comprising at least one multifunctional organic compound in the form of derivatives of aromatic or heterocyclic, or alicyclic, or aliphatic compounds, in an amount of 20 - 40% by weight of the total composition; at least one acidic surfactant in an amount of 2 - 10% by weight of the total composition; at least one trivalent metal compound in an amount of 1.0 - 2.5% by weight of the total composition; sulphuric acid, in an amount of up to 100% by weight of the total composition; a method of its preparation and a method of stabilising clay-loam soils using the stabilising composition.
