Abstract: The out of surface deformation fields around mode I crack tip for brass material are measured by differential interference contrast (DIC) with the help of a Nomarski prism and calculated numerically. On the basis, the characters of out of surface deformation for brass material at macro level and mesoscopic level are analyzed. Out of surface deformation at macro level mainly occurs in the area of 1mm 2 around a crack tip, and the maximum out of surface deformation occurs at the tip of crack. Out of surface deformation at mesoscopic level is closely related to the persistent slip bands (PSB), meso textures and meso structures. Inside a grain, the results of deformation are induced by PSB. There are sudden height changes in PSBs. Among neighboring grains, the successive out of surface deformation depends on the meso structure difference of grains. Out of surface deformation can come across grains. It is also observed during tests that the out of surface deformation in macro shear bands is very apparent.