A group of pyrylium salts with different substituents has been synthesized in this work. Their fluorescence life time

quantum yield and quenching constant by BVE have also been measured. It was found that a strong interaction was observed between BVE and pyrylium salt which contains an electron-withdrawing group

and contrary

the introduction of electron-repulsive groups to the pyrylium salt will decrease this effect. It indicated that these reactions possess the characteristic of electron transfer. Because

the amount of double bond of BVE decreases in the process of BVE polymerization

therefore

in the same time the quenched flu-orescence of pyrylium salt can be recovered gradually. This phenomenon may be used as a probe for studying the process of photo-induced initiated cationic polymerization of BVE.A preliminary mechanism for the photo-initiated polymerization of BVE by pyrylium salt was also discussed.