The invention relates to a selenium rhenium sulfide composite two-dimensional material and a preparation method and application thereof; the preparation method comprises the steps of (a) dissolving ammonium perrhenate and thiourea in an organic solvent to form a first solution; (b) dissolving selenium powder in hydrazine hydrate to obtain a second solution; (c) mixing the first solution and the second solution, and pouring the mixture in a reactor with a substrate to carry out hydrothermal reaction; after the hydrothermal reaction, cooling, and taking out the substrate. By controlling minor doping of sulfur, a selenium rhenium sulfide nanosheet with high coverage, good distribution uniformity and small size is obtained on the substrate, the size of the nanosheet reaches 50-100 nm; the nanosheet with high coverage and vertical growth can provide larger specific surface area, and greater current density is provided in electric catalysis. By adjusting doping quantity of sulfur, the electronic structure of the material is adjusted, hydrogen absorption free energy of the material is lowered, conductivity of the material is improved, more defects and active sites are created, and the electrocatalytic performance of the material is improved.