Abstract: In this experiment the Line LC2 of longan embryogenic callus was used as the material for the study on the changing tendency of Glutathione peroxidase (GPX) activities in the embryogenic callus of longan under the stress of salt (NaCl), light, and temperature. The results showed that: (1) compared with the control, the short-time salt treatment enhanced the activity of GPX, and with the time of stress prolonged, the activities of GPX under low-salt stress treatment ascending first and then descending, while it showed the downtrend under high-salt stress treatment; (2) under the treatment of the white light and green light, with the light intensity increased, the activities of GPX ascending first and then descending, and when the light intensity was the same, the activities of GPX was higher under the treatment of the white light than the green light; (3) under the treatment of low-temperature (high-temperature), with the temperature decreased (increased), the activities of GPX in the embryogenic callus of longan ascending first and then descending compared with those of the control. The above results indicated that under a certain stress, GPX played a role in response to external stimulation, and had a regular expression, and it was one of the main indicators of ROS injury defense under stress.