Finite element analysis of pre-stressed Ultra High-Performance Concrete (UHPC) girders requires careful calibration of constitutive material models. This study presents a systematic sensitivity analysis of the Concrete Damage Plasticity (CDP) parameters within ABAQUS to optimize the finite element model of a full-scale pre-stressed UHPC girder, using comprehensive experimental data on flexural behavior, including moment–deflection, moment–strain relationships, and crack propagation, were available. The sensitivity analysis explored variations in key CDP parameters, including dilation angle (), ratio of the second stress invariant on the tensile median to that of the compressive meridian (Kc), viscosity coefficient (μ), the ratio of equibiaxial compressive yield stress to uniaxial compressive yield (fb0/fc0), and hyperbolic flow potential eccentricity (). The results show that variations in ψ and Kc significantly influence the predicted structural response compared with the other parameters. The optimized parameter set (ψ = 45°, Kc = 0.5, μ = 0.0001, fb0/fc0 = 1.16, and ε = 0.2) used for finite element model validation yielded the closest agreement with experimental results while ensuring numerical stability. This tailored calibration improved the predictive accuracy of the UHPC girder model and ensured stable convergence throughout the simulation stages. The study provides an effective parameter calibration strategy for validating FEM of pre-stressed UHPC structures against experimental benchmarks.