The invention provides a flue gas desulfurization and mercury removal device and method. The device comprises a flue gas channel, an oxidized slurry spraying device, a desulfurized slurry spraying device and a hydrogen sulfide gas jetting device, wherein the flue gas channel is used for providing flue gas; the oxidized slurry spraying device is arranged in the flue gas channel and is used for spraying oxidized slurry into the flue gas channel and oxidizing mercury in the flue gas into divalent mercury; the desulfurized slurry spraying device is arranged in the flue gas channel and is used forspraying desulfurized slurry into the flue gas channel and absorbing SO2 in the flue gas; the hydrogen sulfide gas jetting device is arranged in the flue gas channel and is used for jetting hydrogen sulfide gas into the flue gas channel and converting the divalent mercury into mercury sulfide. By adopting the device provided by the invention, desulfurization and mercury removal combined treatmentcan be carried out on the flue gas at the same time; the device is simple and convenient to operate and the occupied land is saved; the current flue gas desulfurization and mercury removal treatment cost can be effectively improved. Meanwhile, the device has relatively good flue gas desulfurization and mercury removal effects.