The online conductivity meter has the characteristics of full Chinese display, Chinese menu operation, full intelligence, multi-function, high measurement performance and strong environmental adaptability. The conductivity of general liquid can be measured by the secondary meter equipped with electrode with constant of 1.0 or 10; Equipped with 0.1 or 0.01 electrode, it can accurately measure the conductivity of pure water or ultra pure water, especially suitable for on-line continuous monitoring of high purity water conductivity such as boiler feed water and steam condensate in power plant.