Abstract: In order to improve the comprehensive properties of high speed steel, firstly, M2 high speed steel powder is mixed with nano-sized Y2O3 particles by mechanical alloying method, and then Y2O3 dispersion strengthened M2 high speed steel are prepared by selective melting by laser electrometallurgy technology. The effects of Y2O3 particles on the microstructure and mechanical properties of M2 high speed steel prepared by SLM are studied by OM, SEM, EDS analysis and mechanical properties test. The experimental results show that the M2 high speed steel powder after low-energy ball milling is basically spherical, without serious deformation, and the surface is coated with a large number of nanometer Y2O3 particles. The relative density of Y2O3 dispersion strengthened M2 high speed steel samples formed by laser selective melting is 98.3%, and the surface is relatively smooth without obvious cracks, and the top surface quality is better than the side surface. The basic structure and morphology are influenced by the molten pool and the molten channel, and the molten channel shows obvious hexagonal honeycomb grains with fine grains distributed at the edge of the molten channel and slightly larger grains inside the molten channel; The molten pool is mainly composed of equiaxed crystals in the center and columnar dendrite at the boundary, and the grains grow epitaxial along the boundary of the molten pool. Subsequently, the phase of the sample is analyzed, and spikes in BCC and FCC structures are detected in both powder and formed samples, but no peaks of Y2O3 were found in the detection range. The samples of Y2O3 dispersion strengthened high speed steel built by SLM showed good mechanical properties, and the tensile strength reachs 943 MPa, which is 36% stronger than that of high-speed steel without Y2O3 particles. Its fracture surface is flat, and there are a few cleavage steps and columnar crystals, which show brittle fracture. The addition of Y2O3 particles produces more nucleation sites, and refines the grain size of the M2 high-speed steel specimen melted by laser selection. At the same time, Y2O3 particles will also hinder the movement of dislocation and prevent cracks from spreading along grain boundaries during the fracture process, thus improving the mechanical properties of M2 high speed steel.