The　parallel　constrained　groove　pressing　and　the　cross　constrained　groove　pressing　were　imposed　on　a　Cu-38Zn　alloy　sheet　with　different　sizes　numerically　and　experimentally.　The　relationship　between　the　microstructure　and　equivalent　strain　of　the　Cu-38Zn　alloy　was　investigated.　It　is　found　that　the　grain　reduction　of　a　Cu-38Zn　alloy　subjected　to　both　constrained　groove　pressing　is　not　only　related　to　the　accumulated　equivalent　strain　but　also　related　to　the　complexity　of　the　deformation　field　and　the　specimen　size.　With　the　increase　of　the　equivalent　strain,　the　grain　size　of　the　Cu-38Zn　alloy　decreases.　However,　the　cross-orientation　pressing　procedure　results　in　finer　grains　than　the　single-orientation　pressing　procedure　even　though　both　pressings　have　the　same　equivalent　strain.　The　larger　the　specimen　size　is,　the　more　the　twin　in　the　specimen　is.