The invention provides a valganciclovir hydrochloride oral solution and a preparation method thereof, the valganciclovir hydrochloride oral solution is mainly composed of valganciclovir hydrochloride,a solubilizing system, a stabilizing system, a sweetener, an acidity regulator and a preservative; wherein the stabilizing system consists of a complexing agent, an antioxidant and a thickening agent; the contents of valganciclovir hydrochloride, the complexing agent, the antioxidant, the thickener, the sweetener, the acidity regulator and the preservative in the solubilizing system are respectively 7 to 12 percent (W / V), 0.08 to 0.12 percent (W / V), 0.12 to 0.18 percent (W / V), 0.15 to 0.25 percent (W / V), 0.06 to 0.12 percent (W / V), 18 to 22 percent (W / V) and 0.20 to 0.35 percent (W / V). According to the valganciclovir hydrochloride oral solution disclosed by the invention, the raw material medicines can be uniformly dispersed in the liquid solvent; according to the present invention, and are not hydrolyzed, such that the uniform and stable quality is provided, the xanthan gum is added to the acid solubilizing system so as to effectively reduce the degradation degree of valganciclovir hydrochloride, the valganciclovir hydrochloride degradation is less than 1.0% after the long-term sample reserving for 24 months, and the content uniformity RSD is less than 2%.