A preparation method of a wood composite board, comprising following steps: step 1, selecting wood materials and adhesives, wherein the moisture content of the wood materials is 0% -9%, and the adhesive is polyurethane adhesive, formaldehyde-free biomass adhesive or formaldehyde-type adhesives; applying the adhesives into the wood materials and stirring, adhesive consumption is 7%-35% of the weight of the wood materials, applying waterproof agent and mildew preventive into the wood materials, and thereafter drying the wood materials to a moisture content of 3%-15%; step 2, selecting board, evenly coating the adhesives on the upper and lower surfaces of the board, and coating amount of each surface is 100g/m 2 -120g/m 2 , evenly paving the wood materials prepared in step 1 on the upper and lower surfaces of the board, paving amount thereof is 0.5kg/m 2 -3.9kg/m 2 and paving depth is 1mm-3mm; step 3, after the paving in step 2, the wood composite board is made through high-temperature and hot-pressing, hot-pressing temperature is 100°C-150°C, hot-pressing pressure and time are divided into three stages: in the first stage, the pressure is 0.7MPa-0.9MPa for the time of 3-10min, in the second stage, the pressure is 0.3MPa-0.5MPa for the time of 1-10min, in the third stage, the pressure is 0.0MPa-0.3MPa for the time of 1-10min; step 4, after the hot-pressing in step 3, air cooling the wood composite board for more than 5min, and then collecting and stacking thereof; reconditioning the wood composite board naturally for more than 7 days, and trimming and sanding to determine the thickness, the thickness error of the board is controlled in ±0.1mm. step 1, selecting wood materials and adhesives, wherein the moisture content of the wood materials is 0% -9%, and the adhesive is polyurethane adhesive, formaldehyde-free biomass adhesive or formaldehyde-type adhesives; applying the adhesives into the wood materials and stirring, adhesive consumption is 7%-35% of the weight of the wood materials, applying waterproof agent and mildew preventive into the wood materials, and thereafter drying the wood materials to a moisture content of 3%-15%; step 2, selecting board, evenly coating the adhesives on the upper and lower surfaces of the board, and coating amount of each surface is 100g/m 2 -120g/m 2 , evenly paving the wood materials prepared in step 1 on the upper and lower surfaces of the board, paving amount thereof is 0.5kg/m 2 -3.9kg/m 2 and paving depth is 1mm-3mm; step 3, after the paving in step 2, the wood composite board is made through high-temperature and hot-pressing, hot-pressing temperature is 100°C-150°C, hot-pressing pressure and time are divided into three stages: in the first stage, the pressure is 0.7MPa-0.9MPa for the time of 3-10min, in the second stage, the pressure is 0.3MPa-0.5MPa for the time of 1-10min, in the third stage, the pressure is 0.0MPa-0.3MPa for the time of 1-10min; step 4, after the hot-pressing in step 3, air cooling the wood composite board for more than 5min, and then collecting and stacking thereof; reconditioning the wood composite board naturally for more than 7 days, and trimming and sanding to determine the thickness, the thickness error of the board is controlled in ±0.1mm. <EOS>