Abstract: The neutralization research using the 100 MeV proton cyclotron (CYCIAE-100) in China Institute of Atomic Energy was conducted, and a partial stripping technique with thin foils was proposed. Unlike conventional stripping extraction that completely converts negative hydrogen ions to proton beams, a three-component mixed beam of negative hydrogen ions, hydrogen atoms and protons after stripping was produced in this method. The protons reversed rotation direction due to charge inversion and were extracted through the beam extraction channel. The neutral hydrogen atoms moved along tangential trajectory. The unstripped negative hydrogen ions keep circulating and accelerating in the cyclotron. After completing one cycle, they return to the stripping foil and undergo the stripping process again, potentially being converted to protons or hydrogen atoms. If they are still not stripped, they repeat this process until stripping occurs. This research analyzes the evolution of beam composition when negative hydrogen ion beams pass through carbon stripping foils of varying thicknesses. The results show that a single stripping event achieves the maximum neutralization efficiency of 55.95% when using a foil with an areal density of 11.16 μg·cm⁻². For the multi-pass stripping scheme, the neutralization efficiency correlates with the relative ratio of hydrogen atoms to protons generated per stripping event and increases with decreasing foil thickness. However, excessively thin foils not only present fabrication challenges and reduced operational lifetime but also require more circulation turns for complete stripping, consequently increasing beam emittance. After comprehensive evaluation, a 20 μg·cm⁻² foil was selected, achieving 49.3% neutralization within three circulation turns. Multi-particle tracking simulations show the extracted beam distribution characteristics: The proportions of particles stripped in successive turns are 94.0%, 5.7%, and 0.3% respectively. Particles remaining unstripped undergo additional acceleration cycles, where energy accumulation effects increase beam energy spread by 14.3%. Concurrently, inherent longitudinal-radial coupling in cyclotrons causes orbit expansion for high-energy particles, enlarging the radial beam size at the stripping foil by 16.6%. No significant emittance growth was observed axially due to the absence of axial-radial or axial-longitudinal coupling mechanisms. To mitigate beam loss from envelope growth, radial focusing in the extraction region was enhanced through the adjustments of the stripping probe’s position and tilt angle. Positional tuning affects both transverse planes but produces competing effects in horizontal versus vertical focusing, whereas tilt adjustment exclusively modifies horizontal focusing. Optimization prioritized radial focusing due to the predominant radial envelope growth with minimal axial impact. The proton beam profile shows marked improvement, reducing from 4.25 mm (horizontal) × 1.59 mm (vertical) to 2.71 mm×2.10 mm, while the hydrogen atom beam maintains stable dimensions of 2.47 mm×2.26 mm.