A wastewater treatment method using annularly arranged microorganism carriers in a reaction tank, which defines therein an upper reaction area, a lower reaction area and a passage area surrounded by the microorganism carriers and kept in communication between the upper reaction area and the lower reaction area. Microorganisms including nitrifying bacteria and autotrophic denitrifying bacteria are attached to the surface of each microorganisms carriers and suspending in the water of the reaction tank for causing Anammox reaction to convert NH4+ and NO2− in wastewater into nitrogen gas, achieving removal of total nitrogen compounds from water. The microorganism carriers are used to retain microorganisms in the reaction tank, enhancing the treatment efficiency.