Raman spectra of diluted magnetic semiconductor GaMnAs alloy were reported.The coupled plamon-LO-phonon(CPLP) mode has LO-like polarization properties.With increasing Mn concentration,the CPLP mode shifts to low frequency.The hole density in the alloy was determined from the ratio of the intensity of the CPLP mode to that of the unscreened LO mode in the depletion layer.The hole density increases with the increase of the Mn composition.The Raman spectra of GaMnAs alloy were measured at different temperature.It is confirmed that the hole density in the alloy increases with the increase of the temperature.