Objective To determine the therapeutic effect of percutaneous microwave ablation (PMWA) on the elderly patients with liver cancer and investigate the precautionary measures for its complications. Methods A total of 207 elderly patients(>65 years old) with 374 lesions of liver cancer were enrolled in this study. They were divided into 2 groups according to tumor size and number, that is, group A (the tumor diameter less than 4 cm with number less than 3) and group B (over 3 tumors with diameter greater than 4 cm, or a single lesion over 6 cm in size). The patients of both groups were treated with PMWA. The curative effect and complications were observed after surgery, and contrast enhanced ultrasound examination or MR imaging were employed to evaluate the complete ablation. The patients were regularly followed up for 6 to 60 months after treatment. PMWA was carried out again for those with local tumor progression or recurrence. Results In 1 month after PMWA, totally 326 lesions were completely ablated, accounting for 87.2% (326/374). The 1-, 2-, 3-, 4-and 5-year survival rates were 95.3%, 84.6%, 82.5%, 79.2% and 68.8% respectively for group A, and 62.5%, 55.6%, 31.2%, 27.3%, and 0.0% for group B, and significant differences were found between the 2 groups (P=0.021). There were 4 cases (1.07%, 4/374) out of group B having serious complications, including abdominal bleeding in 2 cases and liver abscess in 2 cases. No gastrointestinal and bile duct injury, biliary fistula, or needle tract implantation were found in the subjects. Conclusion PMWA is an effective treatment for liver cancer in the elderly. Tumor size and number, and liver function are main factors for postoperative survival. Ablation needle types, and regimens of power and time are effective measures to prevent the injuries of gastrointestinal tract, bile duct and diaphragm. Postoperative systemic support, anti-abdominal infections and other comprehensive treatment can reduce fatal complications.