Objective: To evaluate the efficacy of percutaneous thermal ablation in treatment of very early stage hepatocellular carcinoma (HCC) and the prognostic factors. Methods: The clinical data of 139 patients with very early stage HCC undergoing ultrasound-guided percutaneous thermal ablation from January 2007 to January 2010 were reviewed. The complete ablation rate, overall survival rate and disease-free survival rate were determined and the influential prognost0ic factors were analyzed. Results: In whole group of patients, the complete ablation rate was 97.84%; the average survival time was (70.10±28.87) months, and the 1-, 3-, and 5-year overall survival rates was 94.90%, 87.70% and 73.10%, respectively; the average disease-free survival time was (44.70±24.21) months, and the 1-, 3-, and 5-year disease- free survival rate was 90.60%, 61.90% and 43.20%, respectively. The results of univariate and multivariate analysis showed that age more than 60 years, disease-free survival time less than 2 years and extrahepatic metastases were independent risk factors for overall survival (all P<0.05); hepatitis C infection and preoperative high AFP level were unfavorable factors for disease-free survival (all P<0.05). Conclusion: Percutaneous thermal ablation is a safe and effective treatment modality for very early stage HCC. However, patients with an old age, short-term recurrence after operation, extrahepatic metastases, high preoperative AFP level and hepatitis C infection may face poor outcomes.