Denitrification by pure and mixed culture of Fusarium oxysporum and Pseudomonas stutzeri in different mineral medium and in synthetic wastewater were examined. The results obtained revealed that a rapid N2 evolution by F. oxysporum and P. stutzeri in mineral medium and synthetic wastewater was observed. In co-cultures of F. oxysporum and P. stutzeri, N2O produced by F. oxysporum was rapidly consumed by P. stutzeri. This indicated that mixed culture of F. oxysporum and P. stutzeri could be used for efficient nitrate and nitrite removal. Using synthetic wastewater, about 87% of nitrate was reduced by co-denitrification of F. oxysporum and P. stutzeri after incubation for 6 days. In the further denitrification tests, the interaction of shell and mixed culture of F. oxysporum and P. stutzeri was investigated. The dinitrogen was rapidly evolved (442.48 micromol N2 produced from 1.0 mmol of NO3(-) in 36 h). These results clearly showed that shell provide a suitable microenvironment for P. stutzeri, which is beneficial to the denitrification.