Quality of epitaxial films strongly depends on their structural and chemical match with the substrates: The more closely they match,the better the film quality is.Topological insulators (TI) such as Bi2Se3 thin films are of no exception.However,there do not exist commercial substrates that match with TI films both structurally and chemically,at the level commonly available for other electronic materials.Here,we introduce BilnSe3 bulk crystal as the best substrate for Bi2Se3 thin films.These films exhibit superior surface morphology,lower defect density and higher Hall mobility than those on other substrates,due to structural and chemical match provided by the BilnSe3 substrate.BilnSe3 substrate could accelerate the advance of TI research and applications.