The invention discloses a conductivity sensor, which overcomes the deficiency of poor identification and measurement capability of conductivity sensors in the prior art for fluid with low conductivity; the sensor comprises a conductivity measuring short section and a sensor electronic short section which are connected by a shielded cable, wherein the conductivity measuring short section is used for establishing an electric field in the fluid to be detected according to an excitation signal, and obtaining a potential difference signal of the electric field at a predetermined measuring distance; the sensor electronic short section is used for generating the excitation signal, applying the excitation signal to the conductivity measuring short section, and obtaining the conductivity of the detected fluid according to the potential difference signal. The embodiments of the invention adopt a contact electrode array, form an electrochemical measuring system with high accuracy, and can overcome underground high-temperature high-pressure severe environment, and the measurement is not influenced by external magnetic fields.