The sensor is an important part of the automatic monitoring equipment of soil moisture，which is the core device that determines theaccuracy of moisture monitoring data. It is very important to scientifically and rationally calibrate the sensor accuracy. Based on the actualproduction，according to the relevant technical specifications and literature results，this paper systematically described the dielectric type soilmoisture sensor formula calibration based on ring knife weighing method, according to the principle that the measured medium apparent sensoroutput signal will change with the soil moisture changing, so as to provide reference for further standardizing the process and technicalrequirements of the laboratory soil moisture sensor, and provide technical support for study on the soil physical characteristics, soil moistureexperiment, and moisture monitoring and evaluation.