Abstract:6 diaryliodonium salts were synthesized by 2 steps reactions.Amon which 4,4′-diacetamidodiphenyliodonium hexafluorophosphate and 3,3′-dinitrophenyliodonium hexafluorophosphate are new compounds.The optimal synthesis conditions of 4,4′-diacetamidodiphenyliodonium hexafluorophosphate was researched.And the result was that when the mole of acetanilide and potassium iodate is 2.2∶1.0, 15 ml acetic acid at 25 ℃ for 24 h, the yield of 47.6% is obtained. The photoinitiability of the 6 products was tested through application .The effect of cationic structure on photodecomposition of various diaryliodonium salts was discussed. It was proved that the 4 products with PF-6 and BF-4 have excellent photoiniotiability and well resistance of oxygen inhibition. When conjugate groups are introduced , ultraviolet spectra of diaryliodonium salt would expend clearly ,of which polymerization is improved.