Simltaeneous treatment of phenol, m-cresol and formaldehyde in wastewater was carried out in a fluidized bed reactor. The response of the treatment unit against the charge of inlet pollutants concentration was measured by changing stepwise the concentration of one component in the mixture. The mutual interaction between each components was qilite different. Simultaneous biodegradation of phenolic compounds and formaldehyde collld be successfully and stably carried out in a three Phase fluidized bed by taking enough residence time.