Problem. On the basis of domestic and foreign research and the analysis of physicochemical properties of elements, the choice of scandium as a microalloying element of high-strength aluminium alloys is substantiated. The main criteria for the ability of scandium and its advantages over transition metals are given. Goal. The purpose of the work is to study the influence of a complex nanomodifier on the change in the structure and mechanical properties of aluminium alloy 1545 of the Al–Mg–Sc system. Methodology. For the first time, the treatment of aluminium melt with a complex nanodisperse modifier of the composition Mg2Si+SiС was proposed. The strength properties of aluminium alloys are significantly influenced by the size of the particles of the strengthening phase. Industrial experiments using dispersed particles of Mg2Si+SiС in a wide range of sizes of 50-100 nm. 
 Results. The technology of modifying aluminium melt with a complex modifier has been developed. Originality. A homogeneous structure of the modified alloy 1545 with a grain size 2.7 times smaller than the original state was achieved. Practical value. In the work, the grain size was determined and it was established that the grain size of alloy 1545 was 15.6 mm2 before modification, and 5.7 mm2 after modification. As can be seen from the given data, as a result of the modification, the grain structure of alloy 1545 was crushed by 2.7 times. It was established that the maximum values of σ0.2 and σv correspond to the optimal content of the powder composition: 0.10% with a further increase of the modifier, the strength properties decrease, while the increase in the strength properties of the modified alloy is 12...18% compared to the initial state.