The biological sponge iron system was acclimated by nitrobenzene simulated wastewater in present study. Meanwhile, the mechanism and the effects of systemic conditions, such as initial concentration of nitrobenzene, sponge iron dosage, initial pH value and temperature, on the degradation of nitrobenzene by domesticated sponge iron system were investigated. The results showed that:compared with the activated sludge system, the biological sponge iron system had a better adaptability and oxidability for degradation of nitrobenzene. The removal rate of nitrobenzene was more than 98% with initial concentration of nitrobenzene at 300mg/L when the biological sponge iron system domesticated to 28th day, and the acclimation cycles was shortened by 28days compared with the activated sludge system. The addition of sponge iron can improve the degradation rate of microbial system. The initial concentration of nitrobenzene and the pH value have an obvious influence on the degradation rate of the system. The suitable temperature range was wider. It can efficiently degrade nitrobenzene from 10 to 40℃. The degradation reaction of nitrobenzene by biological sponge iron system followed zero-order kinetics model. The content of reactive oxygen species (ROS) in the biological sponge system, especially inoculated with iron sludge, was significantly higher than that of in the sponge iron system and the sludge system, which provided stronger Fenton-like effect. Under the optimum conditions, the degradation of nitrobenzene in the biological sponge iron system inoculated with domesticated iron sludge was 31.5min^-1. Besides, the degradation rate of nitrobenzene and TOC were 92.0% and 63.1% respectively, which were 22.3% and 11.4% higher than the superposed values for degradation rates of nitrobenzene in sponge iron system and in iron sludge system alone. This study provides a new idea to treat nitrobenzene wastewater efficiently and economically.