Disclosed is a method and apparatus for determining a tumor ablation margin. The method includes acquiring an angiography image before tumor ablation and an angiography image after tumor ablation when tumor ablation is performed, registering the angiography image before tumor ablation and the angiography image after tumor ablation, and determining the tumor ablation margin according to the relative positions of the tumor area in the angiography image before tumor ablation and the ablation area in the angiography image after tumor ablation after registration. Using an embodiment, one directly determines the tumor ablation margin during tumor ablation, thus improving the efficiency and success rate of tumor ablation.