This paper introduces the design of the device of auto-measuring radon continuously. The core of the system is the design of controlling system by FPGA, which consists of preset module, electrical calendar module and driving module. The system can automatically measure the consistence of the radon and the separating out rate of it. The information data is displayed by LCD. The high speed micro printer is used to print the measuring result. It adopts FPGA to design the measuring system of the device, ...