The invention relates to a method and a 
system for continuously preparing 5-
hydroxymethylfurfural (5-HMF) and a derivative 5-alkoxymethylfurfural (5-AMF) thereof with 
hexose or 
hexose-containing 
biomass as a material. The method takes the characteristic of 
thermal instability in a target product into full consideration and utilizes the characteristic of distinct polarity difference between the product and the material, a reaction unit and an extraction unit are separated in the process of preparing the 5-HMF and the 5-AMF, the 
biomass material reacts along with a polar reaction phase under high temperature and existence of a catalyst, the produced product flows out of reaction environment in time, and after being cooled, the product is extracted and retained by a non-polar extraction phase under normal 
temperature and pressure. The insufficiently reacting material or a polar 
intermediate product is retained in the polar reaction phase, and enters the reaction unit again to form circulation until the reaction is sufficient. In order to increase the distribution ratio and extraction efficiency of the product, a certain amount of inorganic salt can be added into a polar 
solvent. The method and the device effectively increase the selectivity and yield of the target product, and remarkably reduce the 
energy consumption of the whole preparation process. 
Material resources applicable to the method and the 
system are wide, including soluble 
monosaccharide, insoluble lignocellulose and the like. Pickiness about catalysts is avoided, and homogenous and heterogeneous catalysts which are commonly used in such reaction are all applicable to the method and the 
system.