The ultrafast carrier and phonon dynamics of SnSe₂ thin films grown by chemical vapor deposition are investigated based on a self-built ultrafast pump-probe experimental system. By measuring the carrier relaxation process of the SnSe₂ thin films with the variation of pumping energy density, the results showed that the thin films had an ultrafast carrier thermalization process and a composite process on the picosecond to nanosecond time scale. Accompanied by the ultrafast excitation and energy relaxation of photogenerated carriers, the SnSe₂ thin films underwent lattice thermalization and generated coherent acoustic phonons of specific frequencies. The properties of the coherent acoustic phonons generated by the SnSe₂ thin films were revealed by analyzing the variation of the acoustic phonon oscillation signal with the pumping energy density. The results of this study provide reference value for the study of the application of SnSe₂ thin films in the field of optoelectronic devices.