A commercial-purity Zr702 was grain-refined from 20μm to 0.2–0.5μm by equal channel angular pressing. Grain refinement was most evident in the first pass but was insignificant during the subsequent passes. Two microstructural characteristics evolved: a lamellar structure and an equiaxed subgrain structure during the route A pressing and the route B C pressing, respectively. Due to the rotation of specimen in between passes, two sets of geometrically necessary boundaries were formed during the route B C pressing. The mechanism of grain refinement during the route A pressing was evolution of high-angle geometrically necessary boundaries from the low-angled ones, while that during the route B C pressing was decomposition and rearrangement of pre-existing boundaries. The yield stress of severely deformed specimens increased with the reducing grain size according to a Hall–Petch relationship.