The invention belongs to the technical field of building outer wall construction, and discloses a construction method for outer wall surface washed stones. The construction method comprises the following steps: conducting base layer treatment, specifically, plastering or brushing an interface agent on an outer wall to obtain a washed stone wall surface base layer; snapping lines, specifically, snapping grids/dripping sutures on the outer wall; pasting grid division strips and water dripping strips, specifically, arranging the grid division strips or the water dripping strips according to the grids/dripping sutures; brushing cement mortar, specifically, scraping the cement mortar on a wet base layer to form a cement mortar layer; smearing a washed stone slurry surface layer, specifically, smearing washed stone slurry on the cement mortar layer, and kneading, pressing and compacting to form the washed stone slurry surface layer; flushing the surface layer, specifically, after initially setting the washed stone slurry surface layer, flushing the surface of the surface layer by using an under-pressure spray head to expose the washed stones and form a washed stone surface; and forming strips and pointing, specifically, after naturally air-drying the washed stone surface, forming dividing strips and water dripping strips, and conducting pointing through cement and fine sand mortar. The construction method is short in construction period, suitable for large-area outer wall decoration, not prone to stripping, resistant to pollution, free of discoloration and good in economic benefits.