The invention discloses a fire alarm system and method of using multipoint temperature discrete coefficient to predict fiber temperature. The fire alarm method of using multipoint temperature discretecoefficient to predict fiber temperature includes the steps: acquiring Anti-Stokes light and the light intensity numerical value of the Stokes light, the corresponding demodulated temperature numerical value through a distributed temperature measurement system, and determining whether or not satisfying the differential temperature or constant temperature alarm conditions by processing the acquired light intensity and temperature numerical value and comparing the temperature and the light intensity with the alarm threshold; at the same time, by means of the current temperature numerical valueand the discrete coefficients of the temperature of the past plurality of points, predicting the temperature at the next time, and determining whether or not to give an alarm; and if the alarm conditions are satisfied, positioning the alarm position and displaying the alarming time. The fire alarm method of using multipoint temperature discrete coefficient to predict fiber temperature introduces the method of light intensity determination into the differential temperature alarm method, thus effectively reducing the probability of false alarm, and utilizes the discrete coefficients of the current temperature and the past temperature in the pre-determination method of fiber temperature to predict the temperature changing situation in the future, thus effectively reducing the alarm response time.