NOVELTY - A fluidized bed method for synthesizing methane comprises adding catalyst into fluidized bed reactor to form catalyst bed layer, and inputting insert gas to replace gas inside the reactor; heating catalyst bed layer to 200-600 degrees C, and simultaneously adding reducing gas; inputting synthesized gas to fluidized bed reactor from bottom via gas distributor (3); inputting cooling medium into heat-exchanging unit for transferring heat at 200-700 degrees C and 1-70 atm; and introducing reacted gas flow from top of fluidized bed reactor into separating segment, and separating to obtain methane product.    USE - Fluidized bed method for synthesizing methane (claimed).    ADVANTAGE - The equipment exhibits good heat transferring ability and uniform temperature of bed layer; and provides on-line replacement of catalyst, high conversion rate and selectivity, and long continuous running time of catalyst.    DETAILED DESCRIPTION - The fluidized bed method for synthesizing methane comprises:    (A) adding catalyst into fluidized bed reactor to form catalyst bed layer, and inputting insert gas to replace gas inside the reactor;    (B) heating catalyst bed layer to 200-600 degrees C, and simultaneously adding reducing gas to reduce catalyst;    (C) inputting synthesized gas to fluidized bed reactor from bottom via gas distributor (3), where heat-exchanging unit (4) is provided inside barrel body of fluidized bed reactor or outside barrel body of fluidized bed reactor, and synthesized gas is mixed gas of carbon monoxide (CO), hydrogen gas (H2), carbon dioxide, methane, nitrogen gas, steam and hydrogen sulfide;    (D) inputting cooling medium into heat-exchanging unit for transferring heat at 200-700 degrees C and 1-70 atm; and    (E) introducing reacted gas flow from top of fluidized bed reactor into separating segment, and separating to obtain methane product.    An INDEPENDENT CLAIM is included for a fluidized bed equipment comprising reactor barrel body (1), raw material gas inlet (2) and gas distributor located on bottom of fluidized bed, heat-exchanging unit provided inside or outside barrel body, expanding segment (5) located on upper part of barrel body, cyclone separator located inside expanding segment, gas outlet and catalyst feeding hole located on top of expanding segment.    DESCRIPTION OF DRAWING(S) - The drawing is a cross-sectional view showing a fluidized bed equipment.    Barrel body (1)    Gas inlet (2)    Gas distributor (3)    Heat-exchanging unit (4)    Expanding segment (5)