Absorbate-induced thermal faceting is observed by field ion microscopy. Two adsorption systems are investigated: Fe/Pt and Ni/Pt. Pyramids of Fe/Pt tip grow upon {351} consist of {100}、{110}and{111}, while the pyramids grow upon {231} are comprised of {110}、{111}and {311} when anneal the tip to 800~900K. Accordingly, pyramids of Ni/Pt grow upon {231} are composed of {110}、{111}and {311} when anneal to 500~600K.