Using the high-low temperature equipment, we study the influence of temperature on the transmission loss of the large-core optical fiber in the range of -100 ℃ to 100 ℃ by experiment. The experimental results show that the transmission loss coefficient at the first window (850 nm waveband) of the large-core optical fiber fluctuates randomly with temperature. The transmission loss coefficient in the whole temperature range is in the range of 2.543 dB/km to 4.237 dB/km. The results aslo show that, after high-low temperature cycle, the paramagnetic defects are not found in the optical fiber core and the cladding layer, therefore, the chemical bands of the fiber are not broken. In addition, the corresponding stress model is established to explain why the transmission loss coefficient fluctuates too much at the ends of high-low temperature, and the corresponding measures to reduce the effect of the temperature on transmission loss are proposed.