A biomass gas-carbon co-production reactor includes: multiple downward bed pyrolysis zones, a gas-solid separation zone, an activated carbon activation zone, and a secondary pyrolysis reaction zone; wherein the activated carbon activation zone communicates with the gas-solid separation zone and the secondary pyrolysis reaction zone; tops of the downward bed pyrolysis zones penetrate through a top of the gas-solid separation zone, and a heat carrier inlet and a raw material inlet are symmetrically arranged on a left side and a right side of each of the downward bed pyrolysis zones; bottoms of the downward bed pyrolysis zones are located inside the secondary pyrolysis reaction zone for communicating; a fluidizing air inlet is provided at a bottom of the secondary pyrolysis reaction zone, and an activated gas inlet is provided at a top of the secondary pyrolysis reaction zone; an activated carbon outlet is provided on the gas-solid separation zone.