Abstract: The method of differential imaging to detect HIFU-induced lesion combined with lesion evaluation method by measuring the variation of attenuation of soft tissue with log spectral difference algorithm was proposed. Experiment results of bovine muscle and liver in vitro were acquired. The performances of several lesion detection algorithms——Absolute Difference (AD), Sum Absolute Differences (SAD) and Sum Squared Differences (SSD)——were analyzed with several window sizes and threshold values. Then three attenuation parameters to evaluate degree of tissue damage were compared. It is shown that variation of the mean attenuation calculated in the range of bandwidth of transducer △ā is an effective parameter to evaluate lesions.