In　order　to　well　understand　the　role　of　the　accumulative　strain　and　the　effects　of　shear　strain　plane　in　the　grain　refinement　during　constrained　groove　pressing　(CGP),　the　microstructural　evolution　and　the　grain　refinement　rate　of　1060　aluminum　alloy　processed　by　CGP,　such　as　parallel　CGP,　180°　cross　CGP　and　90°　cross　CGP,　were　investigated　by　transmission　electron　microscopy.　The　results　show　that　the　microstructural　evolution　is　independent　of　the　pressing　conditions.　But　the　processing　conditions　significantly　affect　the　grain　refinement　rate,　final　grain　size　and　boundaries　misorientation,　and　the　90°　cross　CGP　is　the　most　effective.　It　is　reasonable　to　conclude　that,　in　the　same　pressing　temperature,　strain　rate　and　accumulative　strain,　the　grain　refinement　rate,　final　grain　size　and　boundaries　misorientation　are　determined　by　the　shear　strain　plane.