Abstract: At present, the determination of field capacity mostly uses traditional manual measurement methods, which have problems such as time-consuming and inability to measure in real time. Therefore, a method based on soil multi-parameter monitoring system to measure field capacity was proposed. The method was based on the experiment based on the natural evaporation of saturated soil moisture content, analyzed the changes of the soil moisture curve at different depths at different stages, and explored the influence of the relative temperature difference of the soil surface on the daily loss of soil moisture. The results showed that the soil moisture curve Y₁ at a depth of 10 cm decreased at different observation stages, and the slope of the curve decreased the most obvious on the 15 th day. The soil moisture curve Y₂ at a depth of 20 cm decreased at different observation stages, and the slope of the curve decreased more obvious on the 12 th day. From the test index of the fitting function of soil volumetric water content and the number of observation days, the determination coefficient R~2 of the regression model was all above 0.99, indicating that there was a quadratic function relationship between the soil volumetric water content of different depths and the number of observation days. The daily loss of soil moisture at different depths showed a one-dimensional cubic function relationship in the time series, and the relative temperature difference of the soil surface was approximately a constant, indicating that the daily loss of soil moisture was less affected by the relative temperature difference of the soil surface. The error of field capacity calculated using the quadratic regression model was 0.05, 0.39, which had higher accuracy. The method provides reference for the application research on soil monitoring equipment in the determination of field capacity.