This study measured the antioxidant enzyme activities of Pyrola under cold and endophytic fungal infection conditions [i.e., peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD)], and the contents of malondialdehyde (MDA), soluble sugar and soluble protein. In addition, the changes in the anatomical structure of Pyrola vegetable organ during cold stress upon inoculation with a synergistic endophytic fungus were also analyzed. It was found that the soluble sugar and soluble protein contents and POD, SOD and CAT activies of Pyrola all increased, when the plants were exposed to temperature of –5℃. In particular, the MDA contents and the POD activies significantly increased compared with those of the control. In addition, the soluble sugar and soluble protein contents increased during the treatment, which involved in both inoculation with an endophytic fungus and low temperature; however, with a reduction in the concentration of endophytic fungus, those two indicators decreased. The optimal concentration of endophytic fungus was 5×107 cfu ? mL-1. From the anatomical structure of Pyrola root, endophytic fungi were found to improve the health of Pyrola in cold weather. These results showed that endophytic fungi played a vital role in the growth of Pyrola, which was an evergreen plant that could survive exposure to low temperature.