The invention belongs to the technical field of photocatalysis, and particularly relates to a preparation method for a visible light ternary photocatalyst. The preparation method comprises the following steps: step 1, adding tetrabutyl titanate into absolute ethyl alcohol, and ultrasonically stirring for 30-60 minutes to obtain a titanate alcohol solution; step 2, slowly dropwise adding ethyl silicate into the titanate alcohol solution, mechanically stirring until completely dissolving to obtain a titanium-silicon mixed alcohol solution; step 3, adding a dispersing agent into ionized water toform dispersion liquid, and slowly adding the dispersion liquid into titanium-silicon alcohol solution to obtain titanium-silicon dispersion liquid; step 4, putting graphene into the titanium-silicondispersion liquid, and performing cyclic ultrasonic reaction for 4-6 hours, thereby obtaining the ternary mixed solution; step 5, putting the ternary mixed solution into a decompression distillation reaction kettle to perform decompression distillation reaction for 60-90 minutes, thereby obtaining a viscous solution; and step 6, putting the thick solution into a drying oven to dry for 30-50 minutes, and heating and sintering for 20-40 minutes, thereby obtaining the ternary photocatalyst. The preparation method solves the problem that performance, in a visible light region, of a graphene-titanium dioxide catalyst is not good; and the prepared photocatalyst is high in stability and photodegradation efficiency.