Liquid-crystal displays (LCD) based on the mini-light-emitting diode (Mini-LED) backlight have attracted significant attention as a promising highly dynamic contrast display system. A halo effect occurs in Mini-LED backlight LCDs because of backlight partition and LCD light leakage, reducing the image quality. In this study, an accurate optical model of the Mini-LED backlight LCD system was established to precisely replicate the halo effect under different parameters. Based on the proposed model, the visual perception experiment of the system was designed to investigate the perception of the human eye on the halo effect under different Mini-LED backlight block sizes, LCD contrasts, and backlight modulation algorithms. The experimental results show that the Mini-LED backlight block size and modulation algorithm significantly influence the halo effect, whereas the LCD contrast has no significant impact on halo effect perception. With an increase in the block size of the Mini-LED backlight, the halo effect is significantly enhanced. When the backlight block viewing angle is 0.5° or larger, the subject can easily perceive the halo effect. In addition, a high linear correlation exists between the subjective experimental results and the objective evaluation results. This study provides a theoretical reference for designing Mini-LED backlight LCD systems.