The invention provides an eco-friendly flexible facing brick prepared from modified waste residues and a preparation method thereof. The eco-friendly flexible facing brick solves the problem that a lot of waste residues are accumulated and severely pollute the environment. The preparation method fully utilizes waste residue characteristics of good compactness and high strength. Through specific treatment, the waste residues are used as aggregate and filling materials in a flexible facing brick. Through pretreatment, the modified waste residues have good stability and can be combined with a polymer well. Compared with the existing flexible facing brick, the eco-friendly flexible facing brick improves ageing resistance and impact resistance.