The effect of stirring strength and t he cooling rate on the rheocast structure of a high chromium white iron were studied.The characteristics of the special low a ngle subgrain boundaries and agglom eration of subgrains were analyzed b y EPMA and EBSD technique.It was found that the cooling rate decid es the ratio of the stress on the dendr ite arm to the diameter of the dendrite root.A proper cooling rate favers the formation of dendrite arm s with big head and thin root and accelerates the breaking of the dendrite a rms.The clustered special subgrain boudaries are the boundaries between the stem and ripened dendr ite arms.The agglomerations of the s ubgrains were indeed evolved from the bent dendrite arms with big h ead and thin root.