To improve the reliability of capacitance prediction for compact coaxial components, a cylindrical capacitor with copper conductors and an air dielectric is modeled and verified by Ansys Maxwell 2D electrostatic simulation. The inner conductor radius is 0.6 mm, the outer conductor inner radius is 1.0 mm, and the outer conductor wall thickness is 0.2 mm. A 1 V potential is assigned to the inner conductor, while the outer conductor is grounded. Based on Gauss’s law, the analytical per-unit-length capacitance is calculated to be 108.9 pF/m. The finite-element model yields 107.4 pF/m, corresponding to a relative error of 1.38%. The simulated electric-field distribution is radially symmetric and reaches its maximum near the inner conductor, which agrees with the theoretical relation E(r) ∝ 1/r. The results show that Maxwell 2D can accurately reproduce the electrostatic behavior of coaxial capacitors and provide an efficient workflow for capacitance extraction, field visualization, and preliminary structural optimization.