The invention discloses a DICOM data-based liver tumor microwave ablation three-dimensional temperature field simulation method, which comprises the following steps: step 1, reconstructing and repairing a tumor and blood vessel model based on DICOM data, introducing the model into a multi-physical field simulation module, selecting a working plane to draw an ablation needle structure chart, and constructing a simulation geometric model; step 2, setting different materials and parameters for a computational domain in the simulation geometric model, wherein the specific material types comprise liver, tumor and PTFE; step 3, constructing a coupling electromagnetic wave radiation model and a biological heat transfer model; step 4, dividing grids for the simulation geometric model according to the model constructed in the step 3 and a set microwave frequency, and setting a solver solving method; and 5, performing visualization processing on the simulation data obtained by solving to obtain temperature field distribution data. According to the simulation method, a three-dimensional finite element simulation model can be established by using preoperative image data of a patient, an ablation thermal field is calculated, and formulation of an operation scheme is guided.