To obtain genetically modified cells which can be used to detect a variety of environmental heavy metals pollution, the fusion gene containing heavy metals induced metallothionein gene MTT1 promoter and exogenousgfpreporter gene was transfected into Tetrahymena thermophilia by biolistic bombardment.By homologous recombination under increasing paromomycin, the genetically modified Tetrahymena with GFP was constructed. With treatment of Cd²⁺,the MTT1 promoter can initiate the correct expression of exogenous gfp gene of the genetically modified Tetrahymena in which green fluorescence can be induced by blue light excitation.The fluorescence response of the genetically modified Tetrahymena with GFP to heavy metals was in order of Cd²⁺,C²⁺,Cr⁶⁺and Hg⁶⁺and Hg²⁺.And the concentration ranges within which fluorescence was induced and with dose-response relationship were both in order of Cd²⁺,Hg²⁺,and Cr⁶⁺.The detection limit of heavy metals was in order of Cr⁶⁺,Hg⁶⁺,Hg²⁺and Cd²⁺. However, the genetically modified Tetrahymena with GFP did not respond to copper. The results showed that the genetically modified Tetrahymena with GFP can be used for detecting Cd²⁺,Hg²⁺,and Cr⁶⁺pollution in environment.