The equal-channel angular (ECA) pressing is most promising technique to produce ultra-fine grained (UFG) materials. Among the parameters of the ECA pressing, processing route, i.e., rotation of a billet around its axis between each pass, has been demonstrated to affect the microstructure development and grain refinement appreciably [1–4]. By the processing route, macroscopic shear plane can be controlled with respect to the texture and microstructure. Thus, it can be assumed that it is not accumulative strain (dislocation density) but an interaction between the shear plane and microstructures that governs the grain refinement [2]. In general sense, however, it is pointed out that during plastic deformation, a high angle grain boundary (HAGB) can be generated by the extension of a pre-existing boundary and/or generation by grain subdividing [5,6]. The former process is strain dependent and therefore high accumulative strain could result in grain refinement whereas the second is a consequence of the crystallographic nature of plastic deformation. ECA pressing can take advantage of the second process. In this context, examining the microstructural development in a single crystalline billet during ECA pressing provides us a deeper insight of (1) the role of pre-exist grain boundary on the grain refinement process by comparing with that of polycrystalline counterpart, (2) grain refinement mechanism from crystallographic viewpoint. In the previous study [7], we found that after eight passes via route C, the microstructure of single crystalline billet was still banded structure whereas that of a polycrystal was equiaxed UFG structure. In the current study, the effect of initial orientation on the grain refinement was examined. The role of interaction between macroscopic shear plane and shear bands was emphasized.