A new pyrene derivative bearing a modifiable silyl function (electron-donating group) and cyano function (electronwithdrawing group) was synthesized as a labelling agent for biological substances. The modified pyrene exhibited a marked bathochromic shift in both absorption and fluorescence spectra. The fluorescence quantum yield of the modified pyrene was also significantly increased compared with that of the unmodified pyrene. The modified pyrene was successfully incorporated into oligoDNA.