The utility model provides a gas water heater, include controller, temperature -detecting device and be used for setting up the pipeline in gas water heater's air outlet department, temperature -detecting device install in on the pipeline, just temperature -detecting device with the controller electricity is connected. This gas water heater has flue temperature detect function, can enough play frost -proof effect, also can play the effect of preventing the dry combustion method, and simple structure, and the precision is high, and it is convenient to maintain, guarantees user's normal use.