High intensity focused ultrasound (HIFU) can irradiate fresh pork in vitro, which causes 3 degrees of lesion of pork tissue. From the aspects of Bmode ultrasound image processing, the research on biological tissue lesion level judgment based on Kmeans clustering and combined with double parameters is proposed in this paper. Realtime Bmode ultrasound images of 134 pork tissues before and after HIFU irradiation can be obtained by B ultrasonic instrument, and they are preprocessed to get digital subtraction images of the focal spot area. Then the gray average and the mean of the wavelet transform coefficient of these digital subtraction images can be extracted. Meanwhile, the pork tissue samples can be classified by Kmeans clustering. The results show that gray average can distinguish the second and the third level of tissue lesion more effectively, and the mean of the wavelet transform coefficient can distinguish the first and the second level of tissue lesion more effectively. However, the method based on Kmeans clustering and combined with double parameters is equipped with the advantages of the two former. And compared the two formers, this method improves the recognition rate of tissue lesion level by 5.23% and 3.43% respectively. And it can judge the lesion level of the pork tissue more accurately. The method can help clinicians to monitor the HIFU treatment process objectively, and it has practical significance to improve the HIFU therapeutic effect.