Provided is a light-switchable gene expression system, comprising: a) a recombinant light-switchable transcription factor-encoding gene, said recombinant light-switchable transcription factor comprising a first polypeptide as the DNA bonding domain, a second polypeptide as the photosensitive domain, and a third polypeptide as the transcription regulatory domain； b) a target transcription unit comprising at least one reaction element recognized and bound by the first polypeptide, a promoter regulated by the third polypeptide and a nucleotide sequence to be transcribed. Also provided is an eukaryotic expression vector comprising said light-switchable gene expression system, and a method for regulating gene expression in a host cell by using the light-switchable gene expression system. Also provided is a reagent kit containing different elements of the light-switchable gene expression system. The light-switchable gene expression system has a quick, effective and powerful induction with little or no toxicity. It is safer than other inducers, and can spatiotemporally control gene expression.
