Zr48Cu36Ag8Al8 bulk metallic glasses with 3 mm diameter were prepared with suction-casting into a water-cooling-copper mold for different casting treatment time from the same overheating temperature. The effect of treatment time in metallic liquid on the mechanical properties of Zr-Cu-based bulk metallic glasses were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), compression tests and scanning electron microscope (SEM). The results show that in a certain range of treatment time, longer treatment time of overheating treatment time would increase the density of the free volume and the deformation ability, thus decreasing the local deformation degree and increasing the fracture strength as well as the plasticity of the Zr48Cu36Ag8Al8 bulk metallic glasses