A heater condition monitoring and accessing method includes steps as follows: A plurality of history operating data of a heater under test are acquired, wherein each of the history operating data has a temperature, an operating sequence, and a resistance. A plurality subsets of the history operating data corresponding to a predetermined temperature range are picked up from the history operating data to form a resistance-operating sequence characteristic curve. At least one test is performed according to the resistance-operating sequence characteristic curve to determine whether a fault of the heater under test occurs at the current operating run or at the subsequent operating run and to evaluate the remaining useful life of the heater under test.