The invention discloses a high temperature resistant plant fiber composite material. The material is prepared by the following components by mass: 100-120 parts of modified flax fiber, 80-120 parts ofmodified soybean fiber and 20-30 parts of waterborne polyurethane resin. A preparation method includes cleaning and crushing the modified flax fiber and the modified soybean fiber to obtain plant fiber powder; placing the plant fiber powder in a high-speed mixer, adding the waterborne polyurethane resin, mixing evenly and stirring to obtain a plant fiber mixed material; heating and molding the plant fiber mixed material and then conducting cold air drying to obtain the material. By means of modified treatment of the flax fiber and the soybean fiber and high-speed mixing with the waterborne polyurethane resin, the resistance of the material to high temperature is enhanced. According to experiments, the high temperature resistant plant fiber composite material has excellent high temperatureresistance while the existing common plant fiber composite material does not have high temperature resistance.