To explore thermoelectric materials is of great significant for energy-saving applications as they can directly convert heat into electricity. As an isostructural compound of newly discovered thermoelectric material FeSb2, FeAs2 also possesses a very large thermoelectricpower of 7mV/K at 12 K. Besides, the thermal conductivity of FeAs2 reached maximum around 20 K and decreased to 10 W/mK at 2 K. The dramatic change of thermal conductivity must be attributed to a variation of the phonon scattering. In order to explore the microscopic features of phonon scattering in related to the variation of macroscopic thermal conductivity, we propose to investigate phonon excitations in the FeAs2 at cold neutron triple-axis spectrometer IN12. The neutron scattering experiment will also apply toprobe the possible anharmonic phonon scattering and possible electron-phonon coupling in FeAs2. We anticipate that our proposed experiment will help us to deduce the underlying phonon behavior and lead to a better understanding of the mechanism which controlsthe thermal conductivity.