The utility model discloses a system for on-line detecting and controlling salt content of soybean sauce. The system includes a soybean sauce pot, detectors I and II which are capable of detecting the salt content of a liquid material, and a salt feeding device, wherein an inlet and an outlet are formed in the soybean sauce pot; the detector I is communicated with the inlet of the soybean sauce pot, and the detector II is communicated with the outlet of the soybean sauce pot; a salt feeding opening is also formed in the soybean sauce pot; the salt feeding device is connected with the salt feeding opening; the detectors I and II are electrically connected with the salt feeding device. According to the utility model, the detectors are additionally mounted at both ends of the soybean sauce pot; by analyzing the salt content at both ends of the soybean sauce pot, the system controls the salt feeding device to add a proper amount of salt into the soybean sauce, thereby realizing precise addition of salt and improving the product quality of the soybean sauce; the system for on-line detecting and controlling the salt content of the soybean sauce is suitable for a salt content monitoring device used during the production process of the soybean sauce.