Abstract: For monitoring soil moisture profile in relation to the root-zones of various crops, an instrument, which could measure soil moisture over a range depth of 0-200 cm, was developed. The principle of soil moisture sensor was based on the fringe-effect of capacitor and the dielectric prosperity of medium surrounding electrodes. When moved up or down in an access tube embedded into soil, the designed probe could sense the moisture profile real-time. The depth transducer consisted of a sensor array of Hall-magnetism components, and a PDA was employed as data-logger. Furthermore, this paper presented the analytical approach on the measurement method, and proposed the experimental method for evaluating the feasibility in the field. Results showed that the system performance index agreed reasonably well with the practical application and it was worthy for recommendation.