1,3,5-Trichloroborazine (TCB) was prepared from the reaction of ammonia chloride with boron trichloride. TCB along with hexamethyldisilazane and boron trichloride were used to synthesize boron nitride (BN) preceramic polymer poly(borazinylamine). This study showed that, the lower the reaction temperature, the higher the synthetic yield. Poly(borazinylamine)＇s solubility mainly depended on the ratio of TCB, (Me,Si)(2)NH, and BCl3. The solvent used in the reaction had a large effect on the ceramic yield of poly(borazinylamine). A soluble poly(borazinylamine) with good synthesis and ceramic yields was obtained when the reaction temperature was -15 degrees C, cyclohexane was the solvent, and the ratio of TCB : (Me3Si)(2)NH : BCl3 was 1 : 6 : 1. By means of infrared and mass spectroscopy analyses, the structure of the poly(borazinylamine) was identified. Thermal decomposition of the poly(borazinylamine) precursor to hydrolyzed BN was also examined. Hydrolyzed BN was obtained at 1000 degrees C, where the ceramic yield was 35-45%.