Adolescent Idiopathic Scoliosis (AIS) is the most common spinal deformity among children and the prevalence of scoliosis is 2-4 % of the general population. Using X-ray images to measure the spine curvature is the most widely used method for quantifying the severity of scoliosis. Unfortunately, X-ray has the radiation hazard and cannot be used frequently for the subjects, particularly for female kids. And this also makes it difficult to monitor the curing effect during the AIS treatment. Therefore, we have developed a novel, radiation-free system for scoliosis evaluation based on 3D ultrasound imaging techniques.