A thin deck water property sensor includes a base, an upper lid, a positive and negative probe, an electric connection element, a processing unit and a display unit. The base and the upper lid are coupled together to form a flat deck. The upper lid has a recess to hold sample water to be tested. The positive and negative probe is extended into the recess in contact with the sample water. The electric connection element has one end connecting to the processing unit and another end coupling with a conductive elastic member. The conductive elastic member is connected to the positive and negative probe. The processing unit receives charged signals of the sample water to generate a test result which is displayed on the display unit.