This invention provides methods for producing ethylene glycol from polyhydroxy compounds such as cellulose, starch, hemicellulose, glucose, sucrose, fructose, fructan, xylose and soluble xylooligosaccharides. The methods uses polyhydroxy compounds as the reactant, a composite catalyst having active components comprising one or more transition metals of Groups 8, 9, or 10, including iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, and platinum, as well as tungsten oxide, tungsten sulfide, tungsten hydroxide, tungsten chloride, tungsten bronze oxide, tungsten acid, tungstate, metatungstate acid, metatungstate, paratungstate acid, paratungstate, peroxotungstic acid, pertungstate, heteropoly acid containing tungsten. Reacting at a temperature of 120-300° C. and a hydrogen pressure of 1-13 MPa under hydrothermal conditions to accomplish one-step catalytic conversion. It realizes efficient, highly selective, high yield preparation of ethylene glycol and propylene glycol from polyhydroxy compounds. The advantage of processes disclosed in this invention include renewable raw material and high atom economy. At the same time, compared with other technologies that converts biomass raw materials into polyols, methods disclosed herein enjoy advantages including simple reaction process, high yield of targeted products, as well as easy preparation and low cost for the catalysts.