This paper presents systematical investigations, including electrochemical activity, MTT cell assay and in vivo test, on the biocompatibility of three metallic glasses. The electrochemical behaviors and the cell toxicity of two newly developed TiZr-based metallic glasses (MGs), Ti42Zr 40Si15Ta3 and Ti40Zr 40Si15Cu5, with lower or without unfavorable elements are systematically investigated. Results show that the MGs with low Cu content exhibit a low electrochemical response. Cytotoxicity tests for the MGs and the mediums after the potential state test are evaluated with in vitro MTT assays. The solid specimens and the mediums after the potential state test for the pure Ti, Ti42Zr40Si15Ta3 and Ti40Zr40Si15Cu5 exhibit no significant cytotoxicity in the MTT test, while the tested medium for Ti 45Cu35Zr20 MG shows lower cell viability. The inductively coupled plasma-mass spectrometry (ICP-MS) results also indicate that the Cu-rich sample released a significant amount of ions which may be the major factor causing the low viability in the MTT test. The good healing condition and the low C-reactive protein (CRP) index for the implanted New Zealand rabbits in a one-month in vivo test also show the satisfactory short-term biocompatibility of the TiZr-based MGs. The electrochemical measurements, in vitro, and in vivo experiments confirm that the developed TiZr-based MGs with lower Cu content (5%) are promising for biomedical purposes.