Abstract: The present invention relates to an injection noncatalyst denitrogen oxide process control system, in which a reducing agent (such as ammonia), carriers and additional gases are injected into the flue gas of a combustion device. The NO.sub.x in the flue gas will be reduced into nitrogen (N.sub.2) and water (H.sub.2 O). A pressure measurement device and a thermocouple device are installed in an injector for measuring the pressure difference and the temperature of the flue gas respectively, and then be converted into a voltage signal and a thermocouple signal respectively. Both of the signals will be transferred into a controller that is controlled by a computer. The controller can control the flow mass of the reducing agent, carriers and additional gases to the flue gas. Therefore, the reduction reaction of the NO.sub.x can be controlled, thereby maximizing the rate of denitrogen oxide (deNOx) and minimizing the discharge amount of the reducing agent.