The invention discloses a bumper lower bar environment-friendly flame-retardant polyurethane foam material and a preparation method. The bumper lower bar environment-friendly flame-retardant polyurethane foam material is composed of acetonitrile polyester and a composite material in a mass ratio of 1:1.7, and the composite material is composed of the following components by mass: 25-28 parts of polyester 403, 35-45 parts of polyester 3360, 250-350 parts of glass fiber, 12-18 parts of polyether 4110, 2.5-3 parts of silicone oil, 1.3-1.8 parts of a catalyst HP-2, 1.5-1.9 parts of a catalyst A33, 3.6-3.9 parts of water, and 36-38 parts of a flame retardant TCEP, wherein the silicone oil is silicone oil AK-158. The preparation method includes: adding the components of the composite material into a reaction kettle and carrying out mixing reaction under a stirring speed of 130-150r/min for 4-5h to obtain the composite material, then mixing acetonitrile polyester and the composite material in a mass ratio of 1:1.7 evenly, thus obtaining the bumper lower bar environment-friendly flame-retardant polyurethane foam material. With the materials and the method provided by the invention, the prepared bumper lower bar environment-friendly flame-retardant polyurethane foam material has the advantages of flame retardance and high temperature resistance, high flame-retardant properties, high strength, long service life and environmental protection.