The dynamics of a polaron on a one-dimensional harmonic lattice in an applied constant electric field has been considered. The calculations were performed with parameters close to those of polyacetylene and DNA. The polaron in a constant field goes to a stationary state, characterized by a constant profile and velocity. In this case, the energy got by the polaron from the electric field is transformed into longitudinal coherent lattice vibrations. For several thousand lattice sites, these oscillations have constant frequency and wave number, and these values depend weakly on the electric field.