A new-type of low density TiAlBeSc alloy system was prepared by vacuum arc melting. The lowest density is 3.289 g/cm3. Its microstructures, thermal stability were studied using SEM (EDS), XRD, nanoindentation and DTA methods. The results show that the TiAlBeSc alloy system forms stable intermetallic compound and solid solution. No transformation occurs below 1000 °C. These alloys exhibit a very high thermal stability with a melting point above 1100 °C. For the equimolar TiAlBeSc alloy, 25% (atomic percentage) beryllium is totally dissolved in scandium lattice. The dendritic TiAl phase with L10 ordered structure is uniformly distributed in α-Sc matrix which exhibits excellent mechanical properties with hardness 7330 MPa.