The invention discloses a method for preparing 5-hydroxymethylfurfural by taking glucose as a raw material, which comprises the steps of: mixing the glucose with water according to the mass ratio of 1: 3-10, loading the mixture into a high-pressure reactor, sealing the high-pressure reactor, increasing the reaction temperature to be between 120 and 250 DEG C, injecting liquid carbon dioxide into the reactor, and controlling the pressure to be between 10 and 25MPa; performing the separation of carbon dioxide and a product on supercritical carbon dioxide with the product dissolved therein through a separator during the reaction, and controlling the separation pressure to be between 5 and 8MPa and the separation temperature to be between 25 and 70 DEG C; and discharging the product from the bottom of the separator, and obtaining a 5-hydroxymethylfurfural product through drying, dehydration and crystallization. The method has the advantages of high selectivity of the 5-hydroxymethylfurfural, continuous production, high product content, green and environment-friendly process, and easy industrialized production.