The invention belongs to the field of pharmaceutical preparation, and particularly relates to a preparation method of valaciclovir hydrochloride. The method comprises the steps of carrying out esterification and condensation on acyclovir and L-valine protected by amino under the action of a coupling agent and one catalyst; carrying out hydrogenating deprotection on a condensation compound under the action of another catalyst; and carrying out acidification through hydrochloric acid to prepare the valaciclovir hydrochloride. The preparation method is simple in process, mild in reaction condition and easy to control, the production efficiency is improved, and the content of the finally prepared valaciclovir hydrochloride reaches 99% or over.