PURPOSE: To obtain the title compound, useful as a raw material and a synthetic intermediate for synthesizing an organophosphazene polymer, at one stage and simply by reacting an organosilylazide compound width a phosphorous diester compound.

CONSTITUTION: An organosilylazide compound (preferably trimethylsilylazide) shown by formula I [R1 to R3 are (substituted) monofunctional hydrocarbon] is reacted with a phosphorous diester compound (e.g. dimethyl phosphite) shown by formula II or formula III [R4 and R5 are (substituted) monofunctional hydrocarbon] preferably in an equimolar ratio optionally in a solvent such as THF at room temperature to 200°C for 30 minutes to 50 hours to give the objective P-hydroxy-N-silyl-phosphazene shown by formula IV.