Most microwave ablation antennas produce a non-spherical ablation zone. We propose a hollow microwave ablation antenna. In the hollow antenna, we use a hollow copper tube as the inner conductor. Compared with the copper core coaxial antenna, the hollow antenna reduces the current on the surface of the outer conductor and produces a spherical ablation zone. We use an internal L-type matching network to design the impedance matching of the hollow antenna. We fabricated the hollow antenna and did the ablation experiments in egg white to verify the ablating ability. The experimental results are similar to the simulated results. The roundness of the ablation zone reaches 86 % at an input power of 20 W and a duration time of 600 s, which shows the ability of the hollow antenna to produce a spherical ablation zone. The hollow antenna can increase the accuracy of microwave ablation and reduce the damage to the normal tissues.INDEX TERMS Microwave ablation antenna, ablation zone, matching network, roundness.