The bulk glassy cylinders with a diameter of 5 mm and the ribbons of 30 μm in thickness of Zr47Ti12.9Cu11Ni9.6Be16.7Nb2.8 metallic glass were prepared by suction casting and melt spinning，respectively. The thermal stability parameters such as glass transition temperature Tg, onset crystallization temperature Tx, glass transition and crystallization activation energies Eg, Ex, etc., were measured by Differential Scanning Calorimetry and the Kissinger equation. The results reveal that the thinner ribbon sample has higher thermal stability and the metallic glass exhibits a “the smaller, the more stable” characteristic. The crystallization behaviors of different size samples also verify the above mentioned characteristic further: in the case of the crystallization of the bulk cylinder being lower than that of the glassy ribbon, the cylinder is crystallized more easily, and its crystallization microstructure is more integral than that of the glassy ribbon.