Objective:To evaluate the availability and security of high-intensity focused ultrasound(HIFU) in the treatment of child hepatoblastoma with the aid of artificial hydrothorax. Methods:Fourteen children(18 lesions)with hepatoblastoma received general anesthesia using trachea cannula. 200-300 ml saline was injected into the right thoracic cavity to turn artificial pleural fluid. Mean invasive arterial pressure(IABP),heart rate(HR),peak airway pressure(Ppeak),compliance of lung(Cmpl),end-tidal carbon dioxide partial press(PETCO2) and oxygen saturation(SpO2) were observed and recorded separately at 5 min after intubation(T0),10 min after establishment of artificial hydrothorax(T1),30 min after HIFU treatment(T2),1 h after HIFU treatment(T3),2 h after HIFU treatment(T4) and at the end of HIFU treatment(T5). Blood gad analysis was made at T0-T5 and 24 h after HIFU treatment(T6). On the 1st d and the 7th d after HIFU treatment,chest X-ray was made to evaluate the hydrothorax and lungs. Before and after HIFU treatment MRI was made to evaluate the availability. Results:During HIFU treatment,all children were steady in various indicators of haemo-dynamics. Ppeak was increased significantly after the establishment of artificial hydrothorax compared with that of T0(P<0.05)and was maintained at the high level;Cmpl was decreased significantly after the establishment of artificial hydrothorax compared with that of T0(P<0.05). PETCO2 was increased significantly after T2(P<0.05);PO2 and PCO2 were both increased significantly after T1(P<0.05). But pH values were not change significantly(P>0.05) and the fluctuations of the respiratory parameters above were all within the safety margin. X-ray showed that artificial hydrothorax was absorbed within 7 d after HIFU treatment. Severe complications like pneumothorax or haemothorax were not ob-served. Postoperative imaging studies(MRI or enhanced CT) prompted all children with lesions reach a predetermined radio frequen-cy ablation effect. Conclusion:HIFU is effective and safe in the treatment of child hepatoblastoma with the aid of artificial hydrothorax.