Abstract: Porous silicon with orange fluorescence was prepared by chemical etching method. The porous silicon particles were characterized by fluorescence spectrum and transmission electron microscopy (TEM). The results showed that the fluorescence intensity was gradually decreased until vanishing after exposed in air for more than one week. The fluorescence luminescence was attributed to the existing of single crystal silicon in the porous silicon. The Hg²⁺ recognition groups were introduced to the surface of porous silicon through thermal reaction and photoreaction forming two chemosensors S₁ and S₂. Mercury ion could be recognized selectively