Electret filters display enhanced ability for particle collection due to its additional electrostatic attraction. However, their efficiency degradation during particle loading remains to be solved. Herein, the loading characteristics of electret filters with neutral particles is investigated via immersed boundary-lattice Boltzmann method (IBLBM). The specific charge distribution on the electret fibers, and the fiber charge decay due to gas neutralization and particle conduction are incorporated in the model. Results verify that the distribution of bipolar charges randomly on fibers with equivalent area is reasonable. The efficiency degradation depends on the proportion of electrostatic collection in the whole particle filtration process, and the attenuation of electrostatic intensity in the electret filter. With the same loaded mass, carbon particles with higher conductivity cause more charge decay and efficiency degradation than NaCl and Al2O3 particles. The fiber charge is mainly lost through conduction, and gas neutralization becomes important only for high-resistivity materials. (C) 2020 Elsevier B.V. All rights reserved.