This paper presents a new kind of meter for water steam overheat temperature. In thermal power plants, the steam overheat temperature is an important parameter for the safe running of the turbine. The parameter is monitored indirectly in most power plants, which may cause severe accidents due to carelessness. The meier solves this problem by a direct overheat temperature display in digits and a automatic safe protection circuit. A storage of the history overheat temperature is also available in the meter for inverstigation of accidents. The principles of measurement and design of the hardware ard software of the meter are discussed and a simple and accurate relationship between the saturated temperature and pressure is established. The equation is applicable to the single chip microcomputer system.