Useful technique to clip designated short RNA fragments from long substrates has been prepared by combining oligonucleotides bearing two acridine groups and lanthanide(III) ions. The substrate RNA is site-selectively activated at two designated phosphodiester linkages by complementary bis-acridine-modified DNA, and is promptly cleaved by lanthanide(III) ions to produce short RNA fragment between the two scission sites. By applying this technique, efficient genotyping method for single nucleotide polymorphism (SNP) have been developed.