A method for preparing a vehicle interior material comprises the steps of feeding 100 parts by weight of phosphorus and nitrogen-containing non-halogen flame retardant particles and 0.1 to 20 parts by weight of hydrophobic inorganic oxide fine particles having hydrophobic groups and having an average particle size of 0.001 to 5 μm to a mixer equipped with a high-speed agitation means having a revolution capability of about 100 to 5,000 rpm, agitating and mixing the phosphorus and nitrogen-containing non-halogen flame retardant particles and the hydrophobic inorganic oxide fine particles to produce the phosphorus and nitrogen-containing non-halogen flame retardant particles coated with the hydrophobic inorganic oxide fine particles, mixing 100 parts by weight as solids of a synthetic resin emulsion and 1 to 300 parts by weight of the phosphorus and nitrogen-containing non-halogen flame retardant particles coated with the hydrophobic inorganic oxide fine particles to produce a coating composition, coating the coating composition onto the vehicle interior material, and drying the coated vehicle interior material.