Spinal sagittal deformity could be frequently observed in adult spinal scoliosis, lumbar degeneration, ankylosing spondylitis, spinal tuberculosis and other diseases. Patients with the spinal sagittal malalignment were often accompanied with sagittal imbalance, cardiopulmonary function abnormity and low back pain. The importance of spinal sagittal morphology in health-related quality of life has been suggested by more and more spinal surgeons. Pelvic backward rotation and knee flexion could be found in patients with severe spinal sagittal deformity. Surgery was essential for advanced stage of spinal sagittal deformity, and the analysis of sagittal alignment based on radiologic methods would be the indispensable part in determining surgical intervention. Sagittal alignment analysis was limited at spine using the conventional radiologic techniques. However, with the progress of study in spinal sagittal alignment, the significant roles of full-body sagittal alignment composed of spine, pelvic and sub-pelvic and dynamic differences in spinal sagittal alignment between various functional positions were being recognized in the evaluation of spinal sagittal alignment. So the evaluation of sagittal alignment would be limited by the conventional imaging. Fortunately, the awkward situation has been retrieved by the innovative EOS imaging system through which both of the full-body sagittal alignment and dynamic spinal sagittal alignment differences could be analyzed. Inspired by the limitation of conventional radiological parameters, a series of new parameters have been adopted to assess the severity of spinal sagittal malalignment. EOS has also been applied to surgical decision making and clinical outcome assessment. This review was to summarize the clinical evaluation of EOS imaging system on spinal deformity along sagittal plane. We hoped to provide new information regarding the global spinal sagittal alignment in different functional posture to improve the understanding of spinal sagittal alignment thereby the optimal surgical strategy could be performed.