*

We report a chemical bonding induced Lifshitz transition of Ti_1-xV_xAl₃ in which the compounds evolve from p-type trivial metal to n-type robust Dirac semimetal. This topological transition is concomitant with an anomalous structural distortion which stems from the interplanar V-Al bond formation. The V-Al bonds in Ti_1-xV_xAl₃ are built up as long as the bonding orbitals of V atoms are fully populated by the electrons. In other words, the type-II Dirac semimetal state of VAl₃ is protected by the V-Al bonds whose molecular orbitals are the “gravity center” of the topological electron and hole bands.