To address the insufficient accuracy of pile foundation settlement calculations in soft soil foundations of port engineering, this study proposes a refined calculation method applicable to soft soil by comparative analysis of differences in Mindlin stress influence coefficients between the national standard JGJ 94-2008 Technical Code for Building Pile Foundations and the Shanghai local standard DGJ 08-11-2018 Design Standard for Foundation Engineering.An improved Mindlin-based model integrating pile diameter and horizontal distance effects is developed through theoretical derivation, overcoming the parameter oversimplification and computational complexity of traditional methods.The results show that pile diameter induces 3%-10% errors in stress influence coefficients near the pile tip (calculation depth z≤3 m), but errors reduce to within 1% when the calculation depth exceeds 3 m.For horizontal distance ρ≥2 m, the computational error between the Shanghai local standard and national numerical integration method is less than 1%.This method enhances settlement calculation accuracy, it can provide efficient support for rigid pile treatments in soft soil foundations of port yard areas, and offer reference and guidance for developing computational programs for pile foundation settlement analysis.