To judge suitability of SOD (Superoxide Dismutase) activity used as one biological indicator to reflect environmental conditions if buried type benthos is used for environmental monitoring or bioremediation, the following uniform experiments were conducted. Rag-worms (Perinereis aibuhitensis), one species of model organisms of ecological toxicology, were exposed to different concentration levels of multiple-contamination of heavy metals, nutrients and petroleum hydrocarbon for 15 days, during which inhabits of rag-worms were simulated by sands and SOD activity were measured. There was no significant difference of SOD activity of rag-worm under different treatments. SOD activity couldn’t be significantly influenced by heavy metals, nutrients and petroleum hydrocarbon. There was no dose-toxicity relation between SOD activity and contaminants. Responses of SOD activity to multiple-contamination were uncertain and SOD activity obeyed Logistic distribution. Thus, whether the SOD activity can be used for the inversion of environmental conditions should be deliberated. As buried type benthos is used for environmental monitoring and bioremediation, it should be cautious to select SOD activity as biological indicator to reflect the environmental conditions .