Abstract: To investigate the effects of liquid injection on the temperature distribution of porous liver during microwave ablation (MWA) in the conditions of different ablation powers and porosities of liver. In this study, an idealized 3D symmetric simplified model of porous media was built to simulate liquid injection combined with microwave ablation on porous liver. Under different porosities of liver(0.10, 0.15, 0.20, 0.25, and 0.30) and different input powers (50, 60, and 70 W) and different injection fluids (saline or anhydrous ethanol) within 300 s, the lesion zones were analyzed. As the porosity increased from 0.10 to 0.30, the ablation area decreased gradually in the non-injection group, and the ablation area of saline group decreased, while that of anhydrous ethanol group increased. However, the ablation area increased or decreased slightly. With the increase of the ablation power (50 to 70 W), the volume of the saline group ablation area increased by 54.99%, 48.73% and 32.71%, compared with that of the group without injection, and the radius expanded from 2.60 to 3.40 cm. As for ethanol, the volume increase rate was 71.68%, 77.99% and 73.39% and the radius expanded from 2.60 to 3.55 cm. The tumor can be completely ablated (d=3 cm). With the increase of the ablation power (50 to 70 W), the ablation volume in saline group increased by 13.89% and 6.19%, respectively. The ablation volume in ethanol group increased by 23.06% and 15.92% with the increase of the ablation power (50 to 70 W). Results show that the lesion zone expands significantly in the condition of liquid injection combined with the microwave ablation. Lesion zone obtained by injection the liquid at the low power (50 W) is superior to the ablation area without injection at the high power (70 W).