Double perovskite structure compounds have gained much attention due to its unusual properties and potential application over single perovskite. However very limited work has been done to understand the lattice dynamics of these compounds. Here we would like to explore the possible relation between charge lattice coupling, half metallic and phonons and the spin-phonon coupling in these compound. Previous Raman measurements draw attention in context of the interplay among lattice, electronic, and spin degrees of freedom. Raman and infra red measurements in the Ba and Sr compounds are limited to the Brillouin zone centre and do not give a complete picture of the dynamics. The aim of our study is to better understand phonon dynamics of A2FeMoO6 (A=Ca,Sr and Ba), in the entire Brillouin zone and over the temperature range of 200-550 K, by characterizing those specific phonon modes relevant to the observed structural distortions and magnetic ordering. Temperature-dependent measurements of phonon spectra and first principles phonon calculations would provide the role of magnetic transition, half mettalicity and structural distortions and and their relationsip to phonons.