The influence of C and B micro-alloying elements on the microstructures and mechanical properties for high Nb containing TiAl alloy was systematically studied. The B micro-addition has a weak effect on the strengthening, but ribbon or dot shaped TiB2 forms at the lamellar colony boundaries and refines the original colony, which is beneficial to improve the room temperature ductility of high Nb containing TiAl alloy. The precipitation of a large amount of Ti3AlC raises the creep resistance during long time creep for high Nb containing TiAl alloy with micro-addition of C.