The dynamic response of a double infinite beam system connected by a viscoelastic foundation under the harmonic line load is studied.The double infinite beam system consists of two identical and parallel beams,and the two beams are infinite elastic homogeneous and isotropic.A viscoelastic layer connects the two beams continuously.To decouple the two coupled equations goving the response of the double infinite beam system,a variable substitution method is introduced.The frequency domain solutions of the decoupled equations are obtained by using Fourier transforms as well as Laplace transforms successively.The time domain solution in the generalized integral form are then obtained by employing the corresponding inverse transforms,i.e.Fourier transform and inverse Laplace transform.The solution is verified by numerical examples,and the effects of parameters on the response are also investigated.