As a strong competitor of the next-generation high-dynamic-range (HDR) display, liquid crystal displays (LCDs) with a minilight-emitting-diode (Mini-LED) backlight are an essential approach for developing new display technologies. LCDs with a Mini-LED backlight inevitably introduce the halo effect because of their structural characteristics, such as local dimming and light leakage. Therefore, to investigate the effect of ambient light on the halo perception of LCDs with a Mini-LED backlight, we propose a fundamental LCD with a Mini-LED backlight simulation model and design a systematic visual perception experiment based on the proposed model. Furthermore, we investigate halo perception under different ambient illuminances, Mini-LED backlight block sizes, and contrast ratios of liquid crystal panels. Additionally, we explore the influence mechanism of ambient light on halo perception based on actual light measurements. The results show that ambient light has a substantial effect on halo perception; ambient light can affect the contrast ratio of the image; and ambient illuminance is negatively correlated with halo perception intensity. Therefore, this study provides a reference for designing and optimizing LCDs with a Mini-LED backlight under different ambient light conditions.