We report a family of novel Strontium (Sr)-based bulk metallic glasses (BMGs) with good glass-forming ability and ultralow glass transition temperature (Tg) by strategic composition design. The Sr-based BMGs can be easily formed with wide composition range by a conventional copper mold cast method. The glassy alloys have many unique and diversified properties such as lowest glass transition temperature, ultralow elastic modulus, small value of Poisson’s ratio and fragility, homogeneous flow at room temperature and tunable water degradation behavior. The BMGs with novel physical and chemical properties could have potential applications for biomaterial and micromanufacture, and are model system for studying some fundamental issues such as crystallization, relaxation and deformation in metallic glass.