BaNi2As2 is metallic compound, susceptible to density-wave formation. Previous studies on BaNi2As2 have revealed the existence of two types of periodic lattice distortion above and below the tetragonal to triclinic structural phase transition (T = 137 K), suggesting Charge-density-wave (CDW) order to compete with superconductivity. In order to study the density-wave formation and determine its origin, we have applied within the framework of this thesis, several experimental methods on high-quality BaNi2As2 single crystals.First, Laue diffraction was used to determine the crystal structure and to orient the BaNi2As2 single crystals. Next, transport measurements of resistivity were undertaken to carefully characterize the samples and investigate the compound’s behaviour at low temperatures, while being exposed to external magnetic field. Those measurements have confirmed the presence of the phase transition (from tetragonal to triclinic phase) at around 130 K upon cooling. Finally, on highest quality samples, time-resolved femtosecond optical spectroscopy was applied. Aim was to reveal the existence of collective CDW amplitude modes and to study their origin. The evolution of these modes through the structural phase transition implies the CDW order in the triclinic phase smoothly evolves from the unidirectional CDW in the tetragonal phase and suggests that the CDW order drives the structural phase transition.