The soil electrical conductivity (EC) refers to the capability for soil to conduct current. It is a comprehensive reflection of soil salinity and moisture. Therefore, acquiring soil EC rapidly and accurately can provide better guidance for farming production. Based on improving four-electrode method, a new portable soil EC detector with six electrodes was developed and its performance was tested. Inside two electrodes and outside two electrodes were used to measure soil EC near the surface and in deeper soil, respectively. And middle two electrodes were used to input a constant current to soil. The stability tests of the current source showed that the amplitude fluctuation was less than 3%.