The effect of yttrium addition on glass formation of a ZrCuAlSi alloy is investigated.The maximum diameter 8mm of the glassy rods for (Zr46.3Cu43.3Al8.9Si1.5)100-xYx alloy with x = 2.5 is obtained by copper mould casting.Apparent enhancement of the glass formation ability is found with addition of yttrium,mainly due to the purification of the alloy melt and the suppression of formation of the primary phases by yttrium.