The decline in walking and postural transition functions in older adults is a critical factor contributing to increased fall risk and reduced independence. This study proposed and validated an assessment method based on a ‘Multi-dimensional Kinematic Profile.‘ This method utilizes radar plots to intuitively present an individual's function across multiple dimensions, including motor efficiency, speed, smoothness, and symmetry, enabling a systematic and individualized quantification of functional deficits in older adults. Healthy older adults (n = 10, 70.3 ± 1.8 years) and healthy young adults (n = 10, 24.4 ± 1.4 years) were recruited for this study. Participants wore inertial measurement units (IMUs) on their lower back and feet while performing a task involving 3-m straight-line walking and a 180-degree turn. This study analyzed Kinematic data of the center of mass (CoM) and correlated with the clinical gold standard, the Timed Up and Go (TUG) test. Compared to the young group, the older group exhibited a significant decline in functional ability during the turning phase. This decline was evidenced by longer turning duration, slower means turning angular velocity, poorer movement smoothness, and lower symmetry. These parameters, which showed significant inter-group differences during turning and were highly correlated with TUG scores, were identified as core kinematic indicators for assessing postural transition ability in older adults. This assessment framework provides a crucial biomechanical basis and evaluation benchmark for designing and optimizing personalized assistive strategies for wearable exoskeletons, holding significant clinical application value.