The invention provides a preparation method of a block WS2 sensitized TiO2 visible light catalyst. A TiO2/WS2 composite photocatalyst is prepared by using a sole-gel-alcohol heating method by adopting block metal sulfide WS2 as a photosensitizer and TiCl4 as a titanium source. According to the method provided by the invention, the block WS2 is adopted to perform sensitization modification on TiO2 directly to form the TiO2/WS2 composite photocatalyst with a special core-shell structure, so that the separation efficiency of photon-generated carriers is promoted, and the photocatalyst has relatively high photo-catalytic activity under the action of visible light. The TiO2/WS2 composite photocatalyst shows good photo-catalytic activity to methyl orange and heavy metal chromium ions under the action of visible light, and has an important application value in purification treatment of organic wastewater and heavy metal wastewater.