NOVELTY - A seaweed biomass is complexly utilized by drying collected seaweed, cutting or crushing into less than 50 mm of length or diameter, sending seaweed with less than 8 mm of length or diameter into pyrolyzing device to perform pyrolyzing; introducing resulting oil gas to separation device after through cooling device, and optionally adding onshore waste biomass to perform co-firing; adding limestone as desulfurization intermediate medium to fuel; calcining limestone in bed to generate calcium oxide; and converting heat energy generated by fuel into steam, and generating ash slag.    USE - Method for complex utilization of seaweed biomass (claimed).    ADVANTAGE - The method is highly efficient and clean achieving desulfurization of more than 90%; and rationally makes use of abundant seaweed resources. The generated ash slag can be used for fertilizer preparation and cement production.    DETAILED DESCRIPTION - The seaweed biomass is complexly utilized by:    (A) drying collected seaweed, cutting or crushing into less than 50 mm of length or diameter, and sieving;    (B) sending seaweed with less than 8 mm of length or diameter into pyrolyzing device to perform pyrolyzing, where heat energy desired by pyrolyzing is from heating furnace, pyrolyzing temperature is 400-700 degrees C, heating up velocity is 100-10000 degrees C/second, and staying time is less than 5 seconds;    (C) introducing generated oil gas to separation device after through cooling device, where separation device divides seaweed oil gas into seaweed bio-oil, fuel gas and fly ash, and storing and using them respectively;    (D) mixing semicoke waste material with sieved seaweed, taking it as fuel for circular fluidized bed boiler, and optionally adding onshore waste biomass to perform cofiring at combusting temperature of 750-850 degrees C;    (E) taking limestone as desulfurization intermediate medium, adding into fuel according to content of sulfur-containing of fuel, where mole ratio of calcium and sulfur in fuel after added limestone is 2-3;    (F) calcining limestone in bed to generate calcium oxide (CaO), reacting CaO with sulfur dioxide (SO2) in smoke to generate calcium sulfate, reducing discharging of SO2;    (G) converting heat energy generated by fuel into steam, sending steam into steam heat supplying device as heat supplying working medium, where heat energy of the steam is changed into kinetic energy via steam turbine, and it drives the dynamo to generate electricity; and    (H) generating ash slag containing sylvite, sodium salt and magnesium, phosphorus and calcium elements.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram illustrating a method for complex utilization of seaweed biomass (Drawing includes non-English language text).