Abstract: The solid-liquid(S/L) intedecial morphology of a single crystal superalloy DD8 has been in-vestigated. The evolutive behavior of cellular morphology with tilted preferred crystallographic orientation near cell-dendrite transition was dynamically observed, and the efFect of crystallo-graphic orientation on primary dendritic arm spacing has been examined. The experimental results show that for planar and cellular morphology no any S/L interfacial anisotropy exists,but near cell-dendrite transition, the S/L intedecial anisotropy appears and gives rise to the cellular crystal fingers tilted from thermal flow direction to preferred crystallographic orientation.The crystal fingers with their preferred orientation parallel to DS growth direction are more stable than that with tilted orientation. For the tilted fingers, the sudece on the side facing DS growth direction is less stable than that on the reverse side, the different stability on the two sides will lead to forming unsymmetrical dendritical microstructure. With the increase of tilted angle of preferred crystallographic orientation, the primary dendrite arm spacing decreases.