Using　surface　mechanical　attrition　treatment　(SMAT),　a　gradient　structure　composed　of　two　gradient　structure　(GS)　layers　and　a　coarse　grain　(CG)　layer　was　generated　from　a　Cu-5.7　wt　pct　Ge　alloy,　significantly　improving　the　yield　strength　of　the　sample.　Unloading-reloading　tests　showed　an　unusual　Bauschinger　effect　in　these　GS　samples.　The　back　stresses　caused　by　the　accumulated　geometrically　necessary　dislocations　(GNDs)　on　the　GS/CG　border　increased　with　increasing　strain.　As　found　by　electron　backscatter　diffraction　(EBSD),　the　GNDs　are　mainly　distributed　in　the　gradient　structured　layer,　and　the　density　of　the　GNDs　increase　with　increasing　SMAT　time.　The　effect　of　the　back　stress　increased　with　increasing　SMAT　processing　time　due　to　the　increase　in　the　strain　gradient.　The　pronounced　Bauschinger　effect　in　a　GS　sample　can　improve　the　resistance　to　forward　plastic　flow　and　finally　contributes　to　the　high　strength　of　GS　samples.