Abstract: Microwave-absorbing ability of granular activated carbon (GAC) and silicon carbide (SiC), and microwave-assisted oxidation of p-nitrophenol (PNP) through the fixed beds of GAC and SiC were investigated. The removal efficiency of PNP with initial solution concentration of 1618 mg•L^-1, reached 96% and 91% of PNP was mineralized onto GAC fixed bed by microwave irradiation, while the highest removal and mineralization efficiency values of PNP were 73% and 24% respectively onto SiC fixed bed for the same PNP solution. Three high concentration PNP solutions (3540, 6858 mg•L^-1 and 11095 mg•L^-1) were treated by microwave respectively through GAC fixed bed and the removal efficiency values of PNP were all higher than 98% and more than 96% PNP was mineralized.The same intermediate products such as o-nitrophenol, phenol and benzoquinone occurred for SiC and GAC during the reaction process, which were degraded further. Biodegradability of the outflow was improved apparently after the treatment by microwave through GAC fixed bed.