Hybrid polyborosilazane (H-PBSZ) was synthesized and characterized. Meanwhile, the curing process of H-PBSZ was analyzed, and H-PBSZ was cured through different processes. Furthermore, the effects of curing pressure on the structure, appearance and apparent density of cured product were investigated. The results show that chemical bonds of B-N, Si-N, B-H, N-H, and Si-H exist in the structure of H-PBSZ. With the increase of temperature, bonds of B-H, N-H, and Si-H will be broken. Large amounts of gases emit from the precursor in the curing process. The density of the cured product is determined by the volume and velocity of the bubbles. The high pressure curing process can reduce the volume of bubbles, decrease their climbing velocity, and restrain the breaking of the bonds containing H atoms, decrease the amount of gases emission in the process. Therefore, much denser cured product is obtained.