Objective To explore the safety of fat reduction treated by non invasive focused ultrasound.Methods A randomized double-blind and negative control clinical trial was carried out on the excess fat of 40 subjects' abdomen by a JCS-01 non-invasive focused ultrasound device.Subjects received treatments with the device on day 1 and day 7.Observations on the area treated and inquiries on feelings were conducted during treatments.Before the first treatment and 14 days after the treatment,laboratory examinations were performed,including liver function,blood lipid tests,etc.Results 40 subjects participated in the trial and 36 subjects (18 each in both treatment and control groups) accomplished 2 times of treatments,all followed-up and laboratory examinations.During the process of treatments,4 subjects in the experimental group complained about feelings of tepidity or pricking.One subject on blood test of triglyceride showed slightly higher than her early normal result,which fell to the normal level at reexamination.Conclusions Subjects treated by non-invasive focused ultrasound at the area of no more than 500 cm2 every time and at an interval of 6 days manifest little changes on the blood test results,with slightly local reactions but no complaints during follow-up.