Objective: To validate a newly designed microwave probe capable of producing larger volume of ablated lesions in ex vivo swine livers. Methods: A novel microwave probe was developed and tested in ex vivo specimens of swine liver. Group A was not given saline infusion under power output 50 W. Group B, C, D under power output 90 W were tested respectively according to the condition of no saline infusion ( group B), 5 min preinfusion ( 5 mlsaline, group C), preinfusion and continuous infusion (at the rate of 1 ml/rmin, group D) using the novel probe. The sizes of the microwave-induced lesions were evaluated and the volume of the tissue destruction qualified. Results: The approximate volumes of the microwave-induced lesions were ( 16.48 ± 3.86) cm3, (28.86 ± 6.15) cm3, (34.11 ± 5.86)cm3, (40.50 ± 10.88) cm3, respectively ( P ＜ 0.01). Preinfusion and continuous infusion (group D) created more spherical lesions than only preinfusion (group C). Conclusion: The newly-developed microwave probe increased the volume of coagulation necrosis, created a more spherical lesion under the power output of 90 W, and might achieve the effective treatment of larger neoplasm with a single application of microwave energy.