A combined sensor for soil moisture content (MC) and electrical conductivity (EC) with 4-ring electrode was developed, based on the dielectric theory. The calibration tests with NaCl solution, moist soil sampler and mixed soil sampler were conducted. The results demonstrated that the combined sensor could response the variation of soil MC and EC. By means of analyzing the outputs of 4-ring sensor in mixed soil sampler, statistical prediction models for soil MC and EC were established, respectively. 