This invention provides a method for catalytic conversion of carbohydrates to low-carbon diols using alloy catalysts. In the process, carbohydrates as the feedstock are subjected to one-step catalytic conversion to realize the highly efficient and selective production of ethylene glycol etc. under hydrothermal conditions, with an alloy catalyst composed of tin, and a transition metal such as iron, cobalt, nickel, rhodium, ruthenium, palladium, iridium, platinum and copper, or a mixture thereof. The reaction is carried out in water at a temperature range of 120-300° C., with a hydrogen pressure range of 1-13 MPa. Compared with the present petroleum based synthesis technology of ethylene glycol, the method in this invention possesses advantages of using renewable feedstock, high atom economy and environmental friendly. Besides, compared with other technologies using biomass as feedstock to produce ethylene glycol, the alloy catalyst in this invention possesses the advantages of few leaching amount, good hydrothermal stability and easy to recycle.