Method for preparing wood-plastic composite by blending heat-treated plant fiber with plastic

The invention relates to a method for preparing a wood-plastic composite, in particular to a method for preparing a wood-plastic composite by blending heat-treated plant fibers with plastics. The method comprises the following steps of: crushing the plant fiber, screening the crushed plant fiber by a sieve of 20-120 meshes to prepare the plant fiber powders; carrying out heat treatment on the crushed plant fiber under an oxygen deficient condition, wherein the heat treatment time is 0.5-24h, the temperature is 140-350 DEG C and the preferably selected temperature range is 180-250 DEG C; uniformly mixing the plastic, a lubricant, a plasticizer, a stabilizer, a compatibilizer and the plant fiber modified by heat treatment to prepare the mixture under the high-speed mixing condition with the rotation speed of 800-1000r/min; and extruding the mixture out of a twin-screw extruder after reaction; and granulating and obtaining granules or directly extruding and obtaining the product by a die. The heat-treated plant fiber powder reduces the amount of hydroxy groups, the hydrophilicity and the water absorption of the final product and improves the dimension stability.