The invention relates to a device and a method for continuously preparing active carbon by a biomass in bulk. The invention is characterized in that the device comprises a spiral dryer (1), a spiral carbonization activation device (2), a spiral cooling device (3), a combustion furnace (4), a waste heat boiler (5), a circulating fan (6), a blower (7), an induced fan (8), a chimney (9), a velocity modulation motor (10), a spray tower (14), a waste liquor circulation pool (15), and a circulation water pump (16), wherein the spiral dryer (1) is provided with a feed port (11), a waste air outlet(1a), a material outlet after drying (13), a coil and a sleeve; and the spiral carbonization activation device (2) comprises a carbonization section (2-1) and an activation section (2-2) communicated with the carbonization section (2-1). By using the invention, the defects of low heat utilization efficiency, low drying / carbonization / activation efficiencies, discontinuous production course and the like in the existing active carbon preparation technology are overcome.