The microstructure evolution of as-rolled Ti-45Al-9Nb-0.3Y alloy as well as the nanohardness of β/B2 matrix was investigated by means of scanning electron microscopy (SEM) in backscattered electron mode (BSE) mode, transmission electron microscopy (TEM) and nanoindentation. This high Nb containing TiAl based alloy was rolled with 50%, 60%, 65% reduction, respectively. Omega phase precipitated in B2 phase with an orientation relationship of {110}β//{11class="imgLazyJSB inlineImage" height="11" width="6" alt="Full-size image (8 K)" title="Full-size image (8 K)" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S1002072116600145-fx2.jpg">0}ω and <1class="imgLazyJSB inlineImage" height="11" width="4" alt="Full-size image (8 K)" title="Full-size image (8 K)" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S1002072116600145-fx3.jpg">1>β//<0001>ω. Moreover, with the increase of deformation reduction, rod-like structure which was formed in γ grain transformed from (α2+γ) lamellae structure into α2 phase only. Additionally, nanoinentation experiment revealed that the precipitation hardening of ω phase increased the hardness of β/B2 phase.