Severe plastic deformation can be achieved in the sample via cyclic channel die compression (CCDC) without changing its shape and size. The height/width ratio is one of the important parameters that affect the CCDC process. A finite element method and experimental validation are employed to investigate the effect of height/width ratio of the sample on compression process, microstructure and properties in this study. The results show that the effective strain is inhomogeneous after deformation. The larger the height/width ratio is, the larger the average effective strain for a single pass compression, and the higher the effective stress. After one pass, grains are squashed, and more serious as the height/width ratio increases. After 3 passes, a large number of shear bands are formed, and become narrow with the increase of height/width ratio. After 12 passes, more equiaxed and finer grains are obtained in the sample with height/width ratio of 2. Hardness of pure copper increases significantly after CCDC, and the hardness value of the sample is higher with height/width ratio of 2.