In this study, electron trapping phenomena in amorphous polymer electrets were studied using a solid-state electron affinity analysis by means of molecular dynamics simulations parametrized with ab initio calculations. Negatively charged amorphous systems of a cyclic transparent optical polymer (CYTOP) with different end groups were reproduced by molecular dynamics simulations parametrized by density functional theory analysis. Quantum mechanical calculations were performed for electron trapping sites to determine the electron affinity of an isolated molecule. The influence of the amorphous system surrounding the trapping site was considered by accounting for electrostatic interactions with surrounding molecules and multipole induction. A series of analyses were carried out to mimic the conformational diversity of the amorphous system. The calculated solid-state electron affinities were found to adopt a Gaussian-type distribution and were in good accordance with the experimental data for surface potential and thermally stimulated discharge spectra, indicating the reliability of the present analysis for predicting the charging performance of amorphous polymer electrets.