The purpose of the study was to prospectively evaluate safety and assisted with ethanol injection for hepatocellular carcinoma abutting gastrointestinal tract. 263 patients with 319 hepatic tumors that underwent percutaneous microwave ablation with curative intention were included. 101 lesions located less than 5 mm from gastrointestinal tract were in gastrointestinal group. 218 lesions located more than 5 mm from hepatic surface, gastrointestinal tract and first or second branch of hepatic vessels were in control group. The temperature of marginal ablation tissue proximal to gastrointestinal tract was monitored and controlled to fluctuating between 45 degrees C and 59 degrees C for more than 10 min for tumors in the gastrointestinal group. Ethanol (1-21 ml) was injected into marginal tissue in 62 of 101 lesions of the G1 group. 96 of 101 tumors (95.0%) in the gastrointestinal group and 208 of 218 tumors (95.4%) in the control group achieved complete ablation (P = 0.89). Local tumor progression for all the tumors were in the first year and the 6-,12- month local tumor progression rate in the gastrointestinal group and the control group were 6.9%, 11.9% and 7.3%, 8.3%, respectively (P = 0.21). There were neither immediate nor periprocedural complications in both groups. There was no delayed complication of gastrointestinal and bile ducts injury. Tumor seeding happened in one (1.1%) of the gastrointestinal group and three (1.8%) of the control group (P = 0.92). Under strict temperature monitoring, microwave ablation assisted with ethanol injection is safe and achieves a high complete ablation rate for hepatocellular carcinoma adjacent to gastrointestinal tract.