Abstract: Objective:To observe the changes of Contrast-Enhanced ultrasonography before and after High Intensity Focused Ultrasound (HIFU) treatment, and evaluate the efficacy of HIFU treatment for transplantable VX2 bone tumor. Methods:Twenty New Zealand white rabbits were inoculated with VX2 tumors in cavitas medullaris of right tibia. HIFU treatment were carried on three weeks after VX2 bone tumors were transplanted. Ultrasonic microbubbles agents were injected to observe perfusion in the treated area and compare the changes of Contrast-Enhanced ultrasonography before and after HIFU treatment. Results:Contrast-Enhanced ultrasonography before HIFU treatment:the tumors in the cavitas medullaris of right tibia were rapidly and obviously perfused with clear boundaries. Average sizes were measured:Vertical diameter was 17.614 ± 0.955 mm and anteroposterior diameter was 10.414 ± 1.142 mm. Contrast-Enhanced ultrasonography after HIFU treatment:treated region was out of perfusion; Average sizes were measured:Vertical diameter was 8.010 ± 0.584 mm and anteroposterior diameter was 7.540 ± 0.499 mm while the untreated region still had microbubbles perfusion. Conclusion:Contrast-Enhanced ultrasound examination can evaluate the efficacy of HIFU treatment in the early stage through the changes of the blood flow in the target region before and after HIFU treatment.