There are less study on instrument parameter adjustment during construction and operation of automatic monitoring systems for soilmoisture. The monitored information can be hardly applied in the draught analysis and assessment because the monitored result precision cannot be improved. By researching, experimenting and summarizing, this paper gave a method of instrument parameter adjustment, and proposedthe view of “improve one line by adjusting one point” during constructing and operating the drought emergency monitoring system inmidwestern region of Jilin Province. The monitoring precision was substantially improved after the new method was used, which met therequirement of the monitoring precision control proposed at the beginning of the project. In this paper, the method of instrument parameteradjustment was summarized, which has important reference value for improving monitoring precision of automatic monitoring systems for soilmoisture and the automation of soil moisture monitoring.