Objective: To study the antioxidant activity and mechanism of mushroom complex polysaccharide (FHP). Method: The free radical scavenging efficiency in vitro and oxidative survival rate in C. elegans were used to evaluate the antioxidant capacity of FHP. The reactive oxygen species (ROS) level， malondialdehyde (MDA) content， antioxidant enzyme activity as well as the stress-related transcription factor activity and effector gene expression were used to study the antioxidant mechanism of FHP. Result: Compared with that of single polysaccharide， FHP exhibited higher free radical scavenging efficiency and stress survival rate increase， indicated a better antioxidant effect. Experiments in C. elegans showed that FHP could not only increase the survival rate of paraquat-stressed N2 nematodes， but also reduce the internal ROS level and MDA content. Further experiments revealed that FHP could also activate the nuclear translocation of stress response transcription factor SKN-1 and DAF-16 and increase that target gene expression， and these results were further verified in the examination of antioxidant enzyme activity. But FHP did not prolong the lifespan and reduce the lipofuscin level in N2 nematodes. Conclusion: FHP can effectively enhance the oxidative stress resistance of C. elegans， but not affect the aging. Its antioxidant mechanism may be related to the activation of transcription factors SKN-1 and DAF-16 and the influence on the downstream effector activity.