Abstract: A method for real-time monitoring in-furnace wall temperature of the high temperature tube systems in utility boilers consists of: Performing pre-calculation and choosing some tubes as representative tubes according the in-furnace tube wall temperature margins in a tube bundle, then installing out-furnace wall temperature measuring points on the chosen tubes; reading data from a power plant real-time database, which are the real-time operational parameters and out-furnace temperatures necessary in the calculation; saving the data into the communication database in local servers; instant calculating the in-furnace steam temperatures and wall temperatures of superheater and reheater tube systems based on the measured real-time operational parameters of the boiler and the out-furnace wall temperatures; sifting out overheated tube segments as per allowable stress, and saving these data into comprehensive overheat database.