The purpose of this study was to examine the degree of disorder of dynamic balance in sitting of stroke patients with hemiplegia by calculation of the area of movements of the center of gravity. Subjects were ten hemiplegic patients. Controls were ten young adults and ten eldery adults. The center of gravity point (mean of Y-axis and mean of X-axis) was measured during movements of the center of gravity toward eight points from the center. An octagon was described on section paper by the eight points. This octagon was divided into six triangles. The area of the octagon was calculated by the sum of the area of six triangles. Moreover, the Heron formula was used for calculation of the area of the triangles. The value of hemiplegic patients was significantly decreased compared to the value of controls. Also, there was a significant difference between eyes open and eyes closed in hemiplegic patients only. This study showed the area of movements of the center of gravity area and its characteristic in sitting of hemiplegia patients.