Ocean temperature monitoring is of great value for the study and protection of marine ecological environment and of great practical significance in preventing the occurrence of marine natural disasters. Traditional electric sensors are difficult to supply power at a long distance, and it is difficult to meet the multiplexing requirements of large-scale sensor networks. Based on the interferometric sensing system platform of weak fiber Bragg grating array, this paper presents an interferometric high precision temperature sensing method which uses phase generated carrier (PGC) algorithm to demodulate temperature signals. In the range of 26.00~30.00 ℃, the temperature phase sensitivity is 1 132.6 rad/℃ and Pearson square correlation coefficient is 0.999 3. Theoretically, the temperature sensitivity can reach 0.000 1 ℃. The results show that the method of demodulation of dynamic signals can achieve high sensitivity detection by applying it to the demodulation of quasi-static signals such as temperature, which has a good application potential in the application of ocean temperature monitoring.