Abstract: Objective : To investigate the effect of low-frequency (0.4 MHz) high-intensity focused ultrasound (HIFU) on the vessels of rabbit VX2 muscle tumor and the growth of tumor. Methods : The VX2 tumor mass was trans-planted into the vastus lateralis of 56 New Zealand white rabbits.Using a random digits table, we divided the rabbits into a control group (Group A) and 3 experimental groups (Groups B, C, and D).The experimental groups received low-frequency HIFU with a sound energy density of 1194, 1592, and 1990 W/cm2 in the B, C, and D groups, respectively.Tumor size was measured at 3 and 7 days after low-frequency HIFU, and the tu-mor growth rate was calculated.We employed color Doppler flow imaging (CDFI) to observe the blood supply of tumors.The tumor tissue was examined pathologically after the animals were sacrificed. Results : At 3 days after low-frequency HIFU, the growth rate of the D group was 13.4-6%, lower than that in the A, B, and C groups ( P <0.05).No statistically significant difference was found in the growth rate among the A, B, and C groups ( P >0.05).CDFI showed that the D group had less tumor blood flow after low-frequency HIFU.No changes were observed in the tumor blood flow in the A, B, and C groups.In all groups, pathological examina-tion showed thrombosis in blood vessels in the interstitial tissues.At 7 days, the tumor growth rate in the C and D groups was 41.9-15% and 25.86%, respectively, both values lower than those in the A and B groups ( P <0.05).CDFI showed that the C and D groups had less tumor blood flow after low-frequency HICU.En-gorgement and congestion were observed in the C group.Most blood vessels of the D group were embolized and had necrosis of tissues surrounding the tumor. Conclusion : HIFU at a frequency of 0.4 MHZ and with a sound energy density of 1990 W/cm² can cause thrombosis in the vessels of rabbit VX2 muscle tumors.Inter-rupting tumor blood supply in such a manner can promote tumor necrosis and delay tumor growth.