In order to explore the temperature adaptability of modulated grating Y-branch (MG-Y) laser in optical fiber sensing application, a test system with wavelength stability of 0.6pm was designed and built. The wavelength characteristics of MG-Y laser at different internal and external temperatures were explored respectively, and the experiments were carried out with a look-up table with an interval of 20pm at 25℃. The results show that 92.30% of the wavelength drift is within ±7pm when the internal temperature is 25℃ and the external temperature is in the range of -20~50℃ and steps by 10℃, and the maximum wavelength drift is 3pm with the internal and external temperature difference of ±5℃. When the external temperature is 25℃ and the internal temperature is in the range of 25~30℃ and steps by 1℃, the mode hopping phenomenon will appear at the switching of the wavelength tuning section. The tuning coefficient range is 85~115pm/℃. It is proved that the optimal temperature of MG-Y laser should be controlled within the range of internal and external temperature difference of ±5℃, which provides a reference for solving the problem of wavelength drift caused by temperature change.