The research and development, preparation technologies, structures and properties of Mg-Ti binary alloys in the recent years are expatiated systematically. It is introduced that mechanical alloying method, physical vapor deposition (PVD) method, high pressure synthesis method and spark plasma sintering method can be used to obtain metastable Mg-Ti binary alloys. And the main factors affecting structural evolvement, hydrogen storage properties, switchable optical properties and mechanical properties of Mg-Ti binary alloys are analyzed. In addition, the pivotal problems in these researches are discussed and the development trend in the future is proposed.