PURPOSE: To provide a peroxide-substd. polysilazane, which does not liberate peroxide during storage, by reacting a high mol.wt. silazane with a hydroperoxide.

CONSTITUTION: A high mol.wt. silazane is reacted with a hydroperoxide shown as ROOH with an effective time and condition to obtain an uncrosslinked polysilazane having a chemically bonded peroxide group. In the formula, R is H, substd. or unsubstd. 1-10C alkyl, 2-10C alkenyl, 2-10C alkynyl, aryl, carboxylic acid or silyl. Preferable polysilazane to be used can be prepared by reacting a mixture of 1-4C alkyl amine or aryl amine substd. or unsubstd. with ammonia with a halogenated silicon like RSiX3 (X is Cl, Br or I).