The invention discloses an electrode type low-conductivity sensor of an MEMS and a measuring method thereof, which belongs to the field of manufacturing of the micro-electromechanical systems (MEMS) and water quality detection. The sensor is composed of an insulating substrate, three planar rectangular electrodes and two pairs of planar interdigital electrodes. All electrodes are arranged horizontally and successively and are distributed in a left-right symmetry mode. The three planar rectangular electrodes that have the same sizes and are distributed at the two ends and the right middle in parallel are used as current electrodes and are used for applying excitation signals. The two pairs of planar interdigital electrodes that have the same sizes and are arranged between the two planar interdigital electrodes in parallel are used as voltage electrodes and are used for detecting response signals. The provided sensor having a simple structure can be operated conveniently. On the basis of the MEMS processing technology, the process is simple; the cost is low; the size is small; and the universality and reliability are high. The sensor can be used for conductivity measurement of low-concentration water.