In order to realize the digital measurement and optimal control in the process of explosive drying, an on-line automatic sampling and detection device for trace moisture is designed. UG_NX 10.0 is used to design and process the on-line automatic detection device. FluidSIM is used to simulate the design of the pneumatic system and verify the action process. OriginPro is used to analyze and function fit the near infrared moisture detection data. SIMATIC WinCC and STEP 7 are used to complete the configuration and operation of the control scheme and process interface. Finally, digital intelligent detection is realized. The application results show that the device realizes on-line detection of trace moisture, man-machine isolation and safe production in dangerous areas.