To investigate their applicabilities as photocurable formulations, photochemical reactions of poly(allylaminophosphazenes) with polythiols of ethylene glycol dimercaptoacetate or trimethylol-propane tri(3-mercaptopropionate) were carried out in the presence of photoinitiators. As a model reaction, hexaallylaminocyclo-triphosphazene(II) was reacted with polythiols, and the thermal properties were investigated. Benzoin alkyl ethers were employed as photoinitiators; in particular, benzoin methyl ether (BME) gave better results in photo reactions. Trimethylolpropane tri(3-mercaptopropionate) was more effective than ethylene glycol dimercaptoacetate in photocrosslinking. The photoreactive system of polyphosphazene containing allyl groups/BME photoinitiator/polythiol was found to be an efficient photocurable system.