The inherent diversity and complex composition of vegetable oils present significant challenges to elucidating the mechanistic pathways involved in sustainable aviation fuel (SAF, C8–C16) production. Octadecane emerges as a critical model compound for probing SAF synthesis mechanisms due to its structural relevance to vegetable oil derivatives. In this work, we establish P-modulated Ni2P1/SAPO-11 for SAF production using octadecane as a representative feedstock. Comparative analysis reveals that the Ni2P1-based catalyst achieves superior C8–C16 yield (69.1%) and i/n ratio (4.5) compared with conventional Ni/SAPO-11, attributable to its optimized charge distribution by P species. Through comprehensive characterization analyses, we demonstrate that the P-modulated Ni active center critically governs the balance between isomerization-cracking reactions. Detailed characterization of the Ni2P1/SAPO-11 clarified the effect of the introduction of P on the charge distribution and acidic properties of Ni/SAPO-11. The resulting SAF product meets critical ASTM D7566 specifications, particularly excelling in low-temperature fluidity (freezing point < –53°C). This work provides valuable insights into acid site engineering for biomass-derived alkane upgrading.