Abstract: Raman scattering spectroscopy is applied to investigate the phonon modes in Ga_xIn_1-xP （x=0.48） and （Al_xGa_1-x）_0.51In_0.49P （x=0.29） alloys in back-scattering geometry. Two-mode behavior in Ga_xIn_1-xP is found. In Ga_xIn_1-xP, the FLA is superimposed on the DALA band. In ordered samples, the GaP-like TO₁ and the InP-like TO₂ are observed.The splitting of LO₁（GaP like） and LO₂（InP like） are believed to be the superlattice effect of ordering. the b/a ratio ranges from 0.40（nominally disordered） to 0.10（ordered）. The small b/a of ordered Ga_xIn_1-xP is affected by the TO₁ mode and LO₂′ splitting of LO₁ mode. （Al_xGa_1-x）_0.51In_0.49P is characterized by its three-mode behavior. the doubling of FLA is found. Due to the influence of Al composition, the GaP-like LO mode becomes a shoulder of the InP-like LO mode. All the phonon modes are consistent with the results of empirical expressions.