The invention discloses a method for continuously preparing 2,5-furandiformic acid by using a microchannel reaction device. The method comprises the following steps that 5-hydroxymethylfurfural and 2,2,6,6-tetramethylpiperidine-N-oxide are dissolved in water, and acetic acid is added dropwise to prepare a homogeneous solution A; sodium bromide and sodium chlorite are dissolved in water to preparea homogeneous solution B; sodium hydroxide is dissolved in water to prepare a homogeneous solution C; the homogeneous solution A and the homogeneous solution B are simultaneously pumped into a first micro-mixer and introduced into a first micro-reactor respectively; the homogeneous solution C and an effluent of the first micro-reactor are simultaneously pumped into a second micro-mixer and introduced into a second micro-reactor respectively, and an effluent is collected to obtain a product. The method for continuously preparing the 2,5-furandiformic acid by using the microchannel reaction device has the advantages that the sodium chlorite is taken as an oxidant, so that the low oxidant price, moderate reaction temperature, higher yield, better target product selectivity and other advantages are provided; the method is simple in operation and low in cost, continuous and uninterrupted production can be achieved, and the industrial application prospect is good.