Abstract: Multiphase flow in porous media represents a fundamental problem in groundwater and environmental studies, with capillary pressure curves serving as the critical constitutive relationship governed by the coupled effects of pore structure, wettability, and multiple other factors. Although traditional models such as the van Genuchten model are widely applied, the correlation mechanisms between their parameters and geomaterial properties remain unclear. Existing scaling methods based on the Young-Laplace equation exhibit theoretical deficiencies and insufficient predictive accuracy when dealing with intermediate wetting conditions (contact angles approaching 90°). This study employed a self-developed microfluidic visualization experimental platform to conduct gas-oil two-phase flow experiments for capillary pressure curve determination, coupled with 500 sets of pore network numerical simulations involving five porosity levels (0.1-0.5) and five particle size variability combinations to systematically investigate the influence mechanisms of pore structural parameters on capillary pressure curves. Results demonstrate that increasing porosity reduces capillary pressure and decreases residual saturation, while particle size variability significantly affects residual saturation under low porosity conditions. Through statistical analysis, quantitative regression equations relating van Genuchten model parameters to porosity and particle size variability were established, and a scaling model based on pore-scale capillary pressure thresholds was proposed, overcoming the limitations of the traditional Leverett J-function under intermediate wetting conditions. The research outcomes, validated through combined experimental and simulation approaches, established a predictive methodology for capillary pressure curves that incorporates pore structural parameters, providing theoretical support for multiphase flow constitutive modeling and subsurface engineering seepage analysis. This work holds significant scientific value and practical guidance for major engineering applications including CO2 geological sequestration and groundwater contamination remediation.