Na2Ti2Sb2O has a CDW transition around 120 K . It has a tetragonal structure with alternate layers of Ti2Sb2O2- and Na+ double layer. Interestingly, the Ba1-xNaxTi2Sb2O system exhibits superconductivity with a maximum Tc of 5.5 K. It is demonstrated that the Fermi surfaces around Gama and X can only overlap with each other with several points,clearly ruling out the Fermi surface nesting as the main source of the CDW transition.On the other hand, a very strong renormalization of the electron mass is found at the CDW wave vector (0.5,0.5), suggesting the presence of very strong electron phonon coupling in this system. In 2H-NbSe2, it has been shown that acoustic phonons soften to zero frequency and become overdamped over an extended region around the CDW wave vector. Similarly, we propose to study the phonon dispersions in Na2Ti2Sb2O and the origin of the CDW phase in this material.