The mechanism and NaOH effect of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl2)(3), with phenol to synthesize the poly(phenoxy)chlorocyclotriphosphazene were investigated by using triphase catalysis in an organic phase/alkaline solution. Four relationships between the ion-exchange reaction and organic reaction were presented and clarified by experimental result. The reaction behaviors varied with different particle sizes of resins. The reaction zone was not the whole resin, and occurred obviously at a shell of the resin when the resin was used larger particle size and higher degree of crosslinkage. The thickness of shell in the resin varied with different NaOH concentrations. The intrinsic reaction kinetics, particle diffusion and film diffusion had to be considered to explain this triphase reaction behavior. The performance of recycle fixed-bed reactor was also investigated.