Air filters with a low resistance, high filtration efficiency, and long lifetime are important to ensure good indoor air quality. In this study, the lattice Boltzmann method is applied on six types of fibrous filter media with lognormal-distribution models, which consider the influence of the solid fraction, number of fibers, and average fiber diameter. The influences of the filtration velocity and fiber layout on the resistance, efficiency, and quality factor are discussed. The resistance is found to be relatively low when the solid fraction inside the filter media is uniformly distributed. The filter media with a random lognormal-distribution model demonstrated the best filtration performance in terms of quality factor. However, when the solid fraction is uniform along the thickness of the filter media, the comprehensive filtration performance is the best when a small fiber is near the inlet and a large one is close to the outlet. This study provides a viable numerical method for performance optimization of air-filtration devices for the next-generation cleanroom industry.