Assuming　that　soil　is　uniform　and　linear　viscoelastic　layer　with　viscous　damping,　soil-pile　interaction　and　the　frequency-domain　torsional　response　of　a　dynamically　loaded　pile　in　the　soil　layer　are　theoretically　investigated.　By　Laplace　transformation,　the　soil　layer　is　studied　first　and　the　vibration　displacement　solution　with　undecided　constants　of　soil　layer　is　used　in　the　analysis　of　pile　response.　And　the　corresponding　solution　of　the　displacement　and　velocity　response　functions　at　the　pile　head　in　frequency　domain　and　the　dynamic　stiffness　of　pile　are　obtained　in　closed　forms.　A　parametric　study　is　conducted　to　determine　the　main　features　of　the　soil-pile　interaction,　and　the　special　influence　of　viscous　damping　of　soil　layer　is　also　discussed.　Finally,　a　comparison　between　the　theories　based　on　plane　strain　assumption　and　the　solution　developed　in　this　paper　is　investigated.