The Raman apectra of phonon and vibron modes in RDX(hexahydro-1,3,5-trinitro-1,3, 5-triazine) and ¦Â-HMX(octahydro-1,3,5,7-teranitro-1,3,5,7-tetrazocine) crystals have been messured at temperatures ranging from 3.8 K to 300.0 K. Shifts in phonon frequency decreased with increasing temperature under high vacuum conditions. It is found that phonons and vibrons have similar averaged lifetime (6.8 ps for phonon modes and 4.0 ps for vibron modes).The bandwidths of phonons and vibrons increased with increasing temperatures. The temperature dependence of bandwidth ⅟ฺ was fitted to a functional form of correct. This temperature dependence was interpreted in terms of three-phonon down process as well as of dephasing processes. Three-phonon and dephasing processes are the dominant relaxation mechanism for most of vibrons.