Microwave ablation is widely used in the treatment of liver tumors because of its minimally invasive and good curative effect. If ablation does not reach the safe margin, it will lead to incomplete treatment and tumor recurrence. Therefore, the evaluation of ablation margin is indispensable. Contrast-enhanced ultrasound has the advantages of economy, real-time, no radioactivity and no nephrotoxicity, which can be used as an important method to evaluate the ablation margin. This article systematically reviews the research progress of contrast-enhanced ultrasound in evaluating the microwave ablation margin of liver tumors.