In this study, we investigated the kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl2)(3), with phenol to synthesize the partially substituted (phenoxy) chlorocyclotriphosphazenes, N3P3Cl6-i(OC6H5)(i), i=1-6 by phase-transfer catalysis (PTC) in an organic phase/alkaline solution. A mathematical model was developed for solving the kinetics parameters for a longer series reaction. The kinetic data of this reaction closely corresponded to a second-order equation by a combined model proposed. The reaction system was controlled by both chemical kinetics and mass transfer effects. Also, the technique of phase-transfer catalysis significantly enhanced the reaction rate. In this reaction, the steric hindrance effect plays a crucial role.