In this work, fiber Bragg gratings (FBGs) are inscribed in seven-core fiber (SCF) based on phase mask technology. The temperature sensing characteristics of seven-core fiber Bragg gratings (FBGs) at room temperature and low temperature are studied by experiments. The results show that the sensor has a temperature sensitivity of 9.98 pm/℃ and a linearity of 0.999 44 in the normal temperature range of 30 ℃~80 ℃. In the low temperature range of -60 ℃~20 ℃, the sensor has a temperature sensitivity of 8.77 pm/℃ and a linearity of 0.997 51. It can be seen that seven-core fiber Bragg grating has relatively stable response characteristics at both normal and low temperatures, but when the temperature decreases, the sensitivity decreases and the linearity becomes worse. The research results have reference value for the research of temperature sensing based on fiber Bragg grating.