Abstract: The ceramization process of polyborosilazane (PSNB), tris(methylamino)borane (PBN) and mixed precursors were studied respectively, and the influence of heat treatment temperature on the microstructure and properties of polymer derived ceramics was mastered. After pyrolysis under NH₃, the B—Si—O—N multielement network was formed in PDC-SiBN, which had good crystallization resistance. After heat treatment at less than 1500℃, the moisture resistance of ceramics was improved, the dielectric constant was between 3.0 and 3.6, and the loss was about 0.003. After pyrolysis under NH₃, the B—N—O structure was formed in PDC-BN, which gradually decomposed into BN with the increase of temperature. The precursor can be mixed in a certain proportion to control the elements of polymer derived ceramics. Due to the existence of heterogeneous interfaces in the mixed precursor derived ceramics, the multiple networks were reduced. The thermal stability and dielectric properties of mixed polymer derived ceramics are between those of single polymer derived ceramics, which have certain performance designability.