Titanium alloy has excellent properties such as low density, high strength and corrosion resistance. It has been widely used in aviation manufacturing fields such as compressor disks and blades manufacturing. However, as the hardness of titanium alloy materials is low, friction loss and other problems are prone to occur during service, which reduces the service life of components. Therefore, in‑situ and real-time hardness monitoring is of great significance for the performance evaluation of titanium alloy components during use. The different hardness of TC4 titanium alloy samples after heat treatment was characterized by laser-induced breakdown spectroscopy (LIBS) in this work. The experimental results showed that the laser-induced plasma temperature of the material increases with the increase of the sample hardness, indicating that laser-induced plasma temperature can be used as an important characterization parameter of metal hardness. Furthermore, the internal mechanism of the influence of material hardness change on plasma temperature was revealed.