Unicellular cyanobacterium metallothionein (MT-like) has been isolated and analyzed comparing with mammal MT. Although there are many differences on their amino acid composition, primary sequence and domain numbers of tertiary structure, their secondary structure and metal-binding properties are similar to each other, showing a kind of function-trending evolution. The MT-like gene: smt-locus has also been cloned and studied about smt A ORF structure, expressional regulation by metal inducing and smt B reverse-transcripted inhibiting, and about the mechanism of the smt genetic amplifi-cation and rearrangment as mammal MT genetic unit. Some questions and focal points about cyanobacterium MT-like studying are suggested.