The humidity sensors of existing technologies are described,and the use of laser scanning technology for humidity detecting new programs is proposed. By scanning the water in the absorption peak at 1.36 μm,a long-term stable detection of humidity is achieved,and the errors and drift can be avoided. The entire system with all-fiber design,achieves a long-range detection. As the probe and signal transmission do not require electricity,the system′s security features are enhanced. The system uses optical devices less susceptible to temperature and stress,making the system more stable even in the high temperature and pressure environment. The design of the humidity detection technology is described in detail,and a humidity detection system is achieved. It reaches the detection of 10-6 -level moisture.