Abstract: Based on the PIP method, the effects of preform structural parameters on the pore distribution, densification process and mechanical properties of carbon fiber reinforced silicon carbide(C_f/SiC) composites were systematically investigated. The evolution mechanism of "rapid weight gain at the initial stage-slow saturation at the later stage" during the sintering process of composite materials was revealed through the statistics of sintering weight gain, macro/micro pore morphology observation and compression-bending property tests, and the exponential decay fitting model was established. The results indicate that the 34-layer specimens demonstrate significantly higher final weight gain rates(135%) during multiple sintering cycles, forming a homogeneous and dense structure that substantially enhanced the material's load-bearing capacity. In contrast, unreasonably structured bending specimens exhibit concentrated porosity due to infiltration limitations, resulting in reduced ultimate strength. This study establishes a comprehensive regulatory mechanism chain of structural parameters- infiltration/sintering-pore distribution-mechanical properties, providing both experimental evidence and theoretical support for PIP process optimization.