Obtaining farmland information quickly and efficiently is the basis of precision agriculture.“Currentvoltage” fourterminal method and time domain reflectrometry (TDR) are two main methods for contact measurement of soil conductivity. A soil conductivity instrument based on the principle of “currentvoltage” fourterminal method was designed, which was calibrated and compared with TDR to explore the applicability of the two methods. The calibration results showed that when the electrical conductivity was in the range of 0 and 14mS/cm, the determination coefficient R2 reached 0.960, and the instrument had high accuracy in this range. The results of soil contrast test showed that the fourterminal method and TDR had good linearity under the condition of low salt content and water content, but when the salt content of sandy loam was more than 0.6%, the change of conductivity measured by fourterminal method tended to be smooth. When the moisture content of silty clay was 20% and 25%, the measurement data of the two instruments were basically the same, so it was needed to try best to avoid measuring when the soil moisture content was high. The comparative experiments under different texture soils showed that the fourterminal method and TDR were greatly affected by the soil type, and the higher the clay content of the soil was, the smaller the conductivity of the soil was. During the test, the fourterminal conductivity meter can measure in real time, but the time of each TDR measurement was about 20s, which was not conducive to realtime measurement.