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Severe plastic deformation (SPD) techniques have attracted significant attention in the last two decades due to its capacity of producing bulk ultra-fine grained (UFG) or nanostructured materials, by imposing very high plastic strain. Equal channel angular pressing (ECAP), or equal channel angular extrusion (ECAE), is one of the most widely used SPD techniques. During ECAP, a sample is pressed through a die which consists of two channels with equal cross-section intersecting at an angle varying from 60° to 150°. Since the cross-section geometry of the sample remains nearly unchanged, the materials can be deformed to a very high strain by repeating the process. The deformation mechanism of ECAP is very complicated and it is dependent on the die geometry and material properties. It has been assumed as simple shear on the intersecting plane of two channels at ideal conditions, such as frictionless, perfectly plastic material and very sharp outer corner. However, from the view of texture evolutions, many experimental results have revealed the deviation from the ideal simple shear. Therefore, an insight into the deformation mechanism and orientation changes in the real ECAP case is still essential. In the present work, a comprehensive study based on the crystal plasticity finite element model (CPFEM) has been conducted to investigate the stress state, plastic strain, required load and crystallographic orientation development history of aluminum single crystals subjected to ECAP. The influence factors such as ECAP die geometry, frictional conditions and initial crystallographic orientations have been studied in detail. [ABSTRACT FROM AUTHOR]