The invention discloses a slightly foaming flame-retardant polyurethane material, and a preparation method thereof. The slightly foaming flame-retardant polyurethane material is prepared from isocyanate, a polycarbonate dihydric alcohol, a filling material, a pigment, a halogen free fire retardant, a flame retardant synergistic agent, a chemical foaming agent, a physical foaming agent, an anti-oxidant, an ultraviolet ray absorber, and a mildew-resistant antiseptic. The preparation method comprises following steps: 1, the polycarbonate dihydric alcohol and the filling material are subjected topre-mixing; 2, isocyanate is added, full reaction is carried out, the pigment, the halogen free fire retardant, the flame retardant synergistic agent, the chemical foaming agent, the physical foamingagent, the anti-oxidant, the ultraviolet ray absorber, and the mildew-resistant antiseptic are added for full reaction. The internal part of the slightly foaming flame-retardant polyurethane materialpossesses uniform micropores; the elasticity is high; the flame resistance, the aging resistance, the mechanical properties, the wear resistance, and the slide resistance are excellent; no smell is observed; the preparation method is safe, is friendly to the environment, is simple, and is convenient for large-scale industrialized production.