The Al-Mg-Mn alloy sheets with and without trace Sc and Zr were investigated by means of tensile test, X-raydiffraction, optical microscope, and transmission electron microscope. The indexes of in-plane anisotropy (IIPA) of their ten-sile mechanical properties were calculated and their inverse pole figures were obtained by Harris method. The two alloysheets have the same law of in-plane anisotropy and remarkable in-plane anisotropy of mechanical properties, and the IIPA ofthe alloy sheet with Sc and Zr is bigger than that of the alloy sheet without Sc and Zr. The relationships of the in-plane ani-sotropy and the anisotropy of the crystallographic texture were analyzed based on the model of monocrystal. It is the com-mon action of the anisotropy of crystallography and microstructures that causes the in-plane anisotropy of their mechanicalproperties, but the major cause is the {110}<112> crystallographic texture. The trace Sc and Zr can promote the formationand stabilization of the {110}<112> texture, inhibit the formation of the {100}<001> texture, and increase the in-plane ani-sotropy of the alloy sheet containing trace Sc and Zr. The indexes of in-plane anisotropy (IIPA) of their ten-sile mechanical properties were calculated and their inverse pole figures were obtained by Harris method. The two alloysheets have the same law of in-plane anisotropy and remarkable in-plane anisotropy of mechanical properties, and the IIPA of the alloy sheet with Sc and Zr is bigger than that of the alloy sheet without Sc and Zr. The relationships of the in-plane ani-sotropy and the anisotropy of the crystallographic texture were analyzed based on the model of monocrystal. It is the com-mon action of the anisotropy of crystallography and microstructures that causes the in-plane anisotropy of their mechanical properties, but the major cause is the {110} <112> crystallographic texture. The trace Sc and Zr can promote the formation and stabilization of the {110} <112> texture, inhibit the formation of the {100} <001> texture, and increase the in-plane ani-sotropy of the alloy sheet containing trace Sc and Zr.