The invention discloses an 
automatic control system and an 
automatic control method for mission monitoring of radioactive airborne effluents. According to the 
automatic control system, an emission flow monitoring sensor is connected with a flow monitoring PLC (
Programmable Logic Controller) through a cable; the flow monitoring PLC is connected with an automatic 
control unit through a 
signal line; the automatic 
control unit is connected with a flow adjusting valve, an 
electromagnetic valve, sampling monitoring equipment, a 
mass flow meter, a pressure gauge and a pump respectively through a 
signal control line; and an airborne substance sampling head is connected with a 
tail gas emission 
pipe after being connected with the flow adjusting valve, the 
electromagnetic valve, the sampling monitoring equipment, the 
mass flow meter, the pressure gauge and the pump respectively in sequence through a sampling 
pipe. Due to the adoption of the automatic 
control system and the automatic control method disclosed by the invention, the sample representativeness of 
effluent monitoring under the conditions of separate or simultaneous emission, large differences among airborne substance source items and scattered emission in a plurality of radioactive operating places can be enhanced, the labor intensity of 
effluent monitoring can be relieved, and the working efficiency is increased; and the 
system and the method have the characteristics of stability, reliability, intelligent regulation and control, and unattended operation.