Abstract: Preclinical studies have confirmed the efficacy of viral vectors as a gene delivery tool，and recent clinical trials have shown promising results with this strategy. But before the clinical application，viral gene vectors should be reconstructed to make it can be regulated in a time- and dose-dependend fashion. Usually，a gene regulation system will be inserted into the vector genome. The tetracycline regulatory system (Tet system) is by far the most frequently used in gene therapy. By adjusting tetracycline or its derivatives (such as doxycyline) in medium or in vivo，the expression of target gene will be switched on or off. The development of Tet system and its application is discussed in this review.

Key words: Gene regulation, Tet system, Gene therapy, Viral vector