Objective To investigate the safety and efficacy of percutaneous microwave ablation (PMWA) for huge liver cavernous hemangiomas(LCHs), and to assess the potential advantages of extracting blood from the hemangioma during the ablation procedures. Methods A water-cooled microwave antenna named KY-2100 compatible with a frequency of 2,450 MHz generator was used to perform heating ablation in 19 patients for their LCHs guided by contrast-enhanced ultrasound under general anesthesia; the patients had multiple LCHs, at least with one having a diameter longer than 6 cm. Twenty lesions matched in their maximal size in 10 patients were ablated assisted with or without extracting blood from the hemangiomas. The relevant factors for the safety and ablation duration, thoroughness of ablation, and complications were comprehensively assessed. Results The ablation durations varied from 39 to 163 min in the 19 patients, with an average of (93±39.85) min. For those maximum-length matched lesions, blood extraction significantly shortened the ablation duration compared to non-blood extraction group (\[29.61±14.07\] min vs \[41.57±14.93\] min, P<0.05). Except for slight elevation of serum ALT level (\[133.58±46.29\] U/L) in 75% patients, there were no other complications such as intra-peritoneal bleeding, bile leakage, or hemoglobinemia. The average hospital stay was (4±0.95) days. All the ablated LCHs shrank markedly, with the maximal diameter decreased by 82.54%. The hemangioma-induced symptoms were relieved in all patients. Conclusion PMWA is technically feasible, safe and effective for treating LCHs. It can be an attractive alternative for surgical resection of hemangiomas at high-risk locations. And prompt extraction of focal blood can reduce the bleeding risk and shorten ablation duration.