The invention discloses a cement plant powder denitration agent conveying device and a use method thereof. The conveying device comprises a material bin, an activation hopper, a pneumatic gate valve,a metering and feeding machine, a weighing spiral conveyor, a gas-solid separator, a feeder, a roots blower and a discharge pipe. The material bin communicates with the activation hopper. The activation hopper communicates with the metering and feeding machine. The pneumatic gate valve is arranged between the activation hopper and the metering and feeding machine. The metering and feeding machinecommunicates with the weighing spiral conveyor. The weighing spiral conveyor communicates with the gas-solid separator. The gas-solid separator communicates with the feeder. The feeder communicates with the discharge pipe. The discharge pipe is connected with the roots blower and a decomposition furnace. Pneumatic arch breakers and a vibrator are arranged on the side wall in the material bin. Thepneumatic arch breakers are arranged on the upper portion and the lower portion of a cylinder section in the material bin and the upper portion of a conical section correspondingly; and meanwhile airhammers are introduced for arch breaking, smoothness of powder discharging is ensured, and the fundamental problem that unsmooth discharging is caused by powder bridging or hardening is solved.