The emission spectrum of a two-level atom in a harmonic trap is studied. It is shown that atomic motion do not affect the atomic spectrum phase sensitivity when there is no correlation between atomic mass center motion and the field. With the increase of the average energy of atomic center motion, the peaks move towards each other, their heights change with the state of the field and atomic motion. When there is correlation between atomic mass center motion and the field, the atomic spectrum becomes insensitive to the relative phase between the field and the atomic dipole. Under certain conditions, there are fewer peaks, and they become higher and narrower.