The utility model discloses a sensor for monitoring the chloride ion concentration and pH value depth distribution in a concrete protection layer. The sensor comprises a base and at least three cylindrical shells which are evenly distributed on the bottom plane of the base and have different heights, wherein first ends of the cylindrical shells are fixedly connected with the base, second ends opposite to the first ends are closed ends, a reference electrode is fixedly arranged at the center of the base, a chloride ion probe and a pH value probe are arranged in each cylindrical shell, one ends of the chloride ion probe and the pH value probe are fixedly arranged at the closed ends of the cylindrical shells and parts of one ends of the chloride ion probe and the pH value probe are exposed out of the surfaces of the closed ends to be taken as detection ends, the other ends of the chloride ion probe and the pH value probe extend in the cylindrical shells and are connected with copper cables which extend out of the cylindrical shells. The sensor can realize the real-time monitoring on the chloride ion concentration and pH value distribution in the concrete protection layer.