In order to monitor the whole process of chloride penetration into concrete and get the chloride concentration at the position of rebar timely and accurately, a solid state chloride sensor which could be embedded in concrete with high sensitivity and stable performance was developed based on the theory of electrochemistry. The results show that Ag/AgCl electrode prepared by pressed powder method has good alkali resistance, short response time, stable performance and good reproducibility. The potential of the electrode is in linear relation with the logarithm of chloride concentration, conforming to Nernst equation. When the temperature is operated at 1040℃, the influence of temperature on the potential value of the sensor can be neglected. But, when the temperature is above 40℃, the temperature influences the potential value of the sensor a lot. A temperature correction coefficient is needed. When 7