The invention relates to a system and method for preparing a reducing gas and activated carbon by pyrolysis of pulverized coal and biomass. The system comprises a sectional type heat treatment unit, a gas purification and separation unit and a mixed semi-coke activation unit, wherein a regenerative type downbed reactor used in the sectional type heat treatment unit comprises a coal pyrolysis zone, a tar catalytic cracking zone and a biomass pyrolysis zone, and the coal pyrolysis zone is provided with a pulverized coal inlet and a semi-coke outlet; the biomass pyrolysis zone is provided with a biomass inlet and a biomass coke outlet, and the tar catalytic cracking zone is provided with a pyrolysis mixed gas outlet; and the gas purification and separation unit comprises a pyrolysis mixed gas inlet, a syngas outlet, a fly ash outlet and a carbon dioxide outlet, and the mixed semi-coke activation unit comprises a high temperature mixed semi-coke inlet, a carbon dioxide inlet, an activated carbon outlet and an activated carbon dioxide outlet. The technical scheme provided by the invention can make full use of heat carried by a pyrolysis gas, solve the problem of tar utilization, and realize the efficient and comprehensive utilization of high temperature pyrolysis semi-cokes.