The invention relates to a method for preparing 5-hydroxymethylfurfural (HMF) by transforming a biomass saccharine source. The method comprises the following concrete steps: using an ionic liquid as a solvent, hexose or hexose source biomass as a raw material substrate, and acid as a catalyst, heating the mixture to react for 5 minutes to 20 hours at normal pressure, and then depressurizing and distilling the mixture under the condition that an operation temperature is not higher than 180 DEG C to obtain the HMF after the reaction is ended; and after the distilled remainder is cooled, directly adding the remainder into the biomass saccharine source, and repeating the processes of reaction and separation to obtain the HMF, so as to realize recycling of an ionic liquid catalyst system and semi-continuous preparation of the HMF. By using the method, once through yield of the HMF reaches as high as 94 percent. The method has the advantages of high selectivity, low acid consumption, mild condition, quick reaction, reusability of the ionic liquid, low cost, simple process, environmental protection, semi-continuous production and the like, and provides new technology for industrialized production of the HMF by transforming the biomass saccharine source, so as to develop a new path for preparing common chemicals in a large scale by using biomass resources and replacing fuels.