The Raman spectra of the SiC layers in TRISO particles of fuel elements of HTGRs are studied. Through the analysis of the Raman shifts, the FWHM and intensities, the crystal phases, the residual stress and densities of SiC layers and corresponding spectroscopic features are clarified. The study of the 2D correlation spectrum of first order Raman scattering of SiC layer shows that the LO mode is much more sensitive than the TO mode to the change of density of SiC layer. All these conclusions are significant for synthesising TRISO particles and fuel elements of HTGRs and estimating their qualities.