The investigations of the phase constitutes and microstructure were performed on as-cast (Ti 40 Zr 25 Ni 8 Cu 9 Be 18 ) 100−x Nb x (x=0, 3, 5, 8, 10) (Ø 3) glass forming alloys. Large quantities of icosahedral quasicrystals are found to distribute in the glassy matrix of alloys with Nb content 3 and 5at.%, fully amorphous phase with 8at.% Nb, and a few nanocrystals corresponding to a CuTi-phase precipitating in the glassy matrix with 10at.% Nb. In addition, 8at.% Nb-containing alloy exhibits relatively good glass forming ability as well as Nb-free alloy. The activation energy for the first crystallization of this alloy is 249.80kJ/mol, larger than that of the Nb-free alloy; moreover, this alloy possesses higher room temperature compressive fracture strength (2083MPa), although it exhibits smaller plasticity (2.1%) than that of Nb-free alloy.