The invention relates to a chimney gypsum rain real-time monitoring system based on water balance in a thermal power plant, which comprises a data monitoring center, wherein the data monitoring centeris in communication connection with an original flue gas water quantity monitoring subsystem, a wet desulfurization section flue gas water quantity monitoring subsystem and a chimney section flue gaswater quantity monitoring subsystem; the original flue gas water quantity monitoring subsystem comprises a flow measuring instrument, humidity measuring instrument and temperature measuring instrument which are arranged on an original flue channel connected with a desulfurization tower, the flow measuring instrument, the humidity measuring instrument and the temperature measuring instrument are connected with a data processing control system; the wet desulfurization section flue gas water quantity monitoring subsystem comprises a flow measuring instrument, humidity measuring instrument and temperature measuring instrument which are arranged on a flue channel between the desulfurization tower and a chimney; the flow measuring instrument, the humidity measuring instrument and the temperature measuring instrument are in communication connection with the data processing control system; the chimney section flue gas water quantity monitoring subsystem comprises a temperature measuring instrument arranged on the chimney. According to the invention, the wireless communication technology is utilized for data transmission, so that the operation cost is saved.