Provided is an antenna assembly for microwave ablation, comprising: a radiator for emitting a microwave for ablation； a coaxial cable for transmitting the microwave for ablation generated by a microwave generator to the radiator； characterized in that an annular composite structure for inhibiting an electromagnetic wave propagated backwards along the coaxial cable is provided around the coaxial cable, wherein the annular composite structure comprises an annular nonmetallic layer and an annular metallic layer located outside the annular nonmetallic layer, wherein the annular metallic layer is electrically insulated from the coaxial cable. Provided also is a microwave ablation needle using the same. The annular composite structure of this disclosure may inhibit effectively the backward propagation of the microwave along the coaxial cable exterior wall. It is not required to fill any stabilizing medium in the radiation zone. The circulation water is allowed to enter the radiation zone, so that the temperature of the head the ablation needle may be controlled effectively, so as to avoid burnout of the ablation needle and medical accident due to an excessively high temperature.
