The temperature dependence of viscosity of the bulk metallic glass Zr41Ti14Cu12.5Ni10Be22.5（Vit1）under constant heating condition was obtained by application of static extension measurement. A few strain rate peaks, which are associated with the glass transition and multistep crystallization, were observed in the temperature-strain rate curve. Above the glass transition temperature, the supercooled liquid of the bulk metallic glass showed the Newtonian rheological characteristic, and its temperature dependences of viscosity in supercooled liquid region can be fitted well with the Vogel-Fulcher-Tammann(VFT) equation. The sample exhibited the fragility parameter D* value of 36, the VFT temperature T0 of 319K and the fragility m value of 30 It was shown that the Vit1 alloy is a strong liquid, similar to sodium silicate liquids. However, the relation between temperature and viscosity deviated from VFT equation below the glass transition temperature.The phenomenon is tentatively interpreted in terms of free-volume model and structure relaxation concept.