Objective To achieve real-time monitoring of microwave ablation for liver tumor, a detection method of microwave ablation zone based on ultrasound echo decorrelation imaging was proposed in this study.Methods In this study, 15 porcine livers in vitro ( P = 80 W, t = 60 s) were carried out in the microwave ablation experiments. The ultrasound echo signals at different times during microwave ablation were continuously acquired at a rate of 2 frames/s using the self-writing program. The instantaneous decorrelation imaging of each two adjacent frame ultrasound data was calculated respectively, and the maximum values of all the pixels in all the instantaneous decorrelation images were used to form cumulative decorrelation image, followed by logarithm compression. The threshold as-0. 4 and polynomial approximation were used to detect the thermal lesions in the cumulative decorrelation image. The long axis and short axis of the ablation zone were measured and recorded, and the area was calculated. The actual thermal lesion in the tissue section of the porcine liver after ablation was used as the gold standard to evaluate the accuracy of this algorithm. Results Compared with B-mode images, there was a larger contrast between thermal lesions and normal liver tissues in the instantaneous decorrelation image, which could be used to monitor the real-time change of coagulation during thermal ablation. The results of 15 cases of thermal ablation zonedetection showed that the average accuracy of the cumulative decorrelation imaging for detecting the microwave thermal lesions was 88. 60%. Conclusions The technique of ultrasound echo decorrelation imaging can achieve quantitative real-time monitoring of microwave ablation of liver in vitro.