The invention provides a silver sulfide/titanium dioxide nanobelt photocatalyst and a preparation method thereof. During the silver sulfide/titanium dioxide nanobelt photocatalyst preparation, firstly, a silver nitrate solution and titanium dioxide are fully dissolved into deionized water to prepare first mixed liquid; then, a sodium sulfide solution is added into the first mixed liquid; the mixture is fully stirred to prepare second mixed liquid; next, the second mixed liquid is put into a hydrothermal reaction kettle for preparing third mixed liquid; next, the third mixed liquid is filtered to obtain precipitates; finally, the precipitates obtained through separation are washed and are subjected to vacuum heat preservation to prepare the silver sulfide/titanium dioxide nanobelt photocatalyst. The prepared silver sulfide/titanium dioxide nanobelt photocatalyst has the advantages that the specific surface area is great; good sunlight full-wave band photocatalytic activity is realized; the utilization rate of light-catalyzed reaction on sunlight is improved; the utilization range of the sunlight is expanded.