NOVELTY - The preparation method of three-dimensional graphene/tungsten-based nanosheet/magnesium-doped zinc oxide layer-by-layer assembly structure, involves adding tungsten powder and cetyltrimethylammonium bromide to deionized water, ultrasonically dispersing to obtain tungsten-based dispersion liquid, shearing tungsten-based dispersion liquid, centrifuging to obtain tungsten nanochip solution, adding graphene solution to deionized water, ultrasonically dispersing to obtain graphene dispersion (1), adding anionic surfactant to dispersion (1) and ultrasonically dispersing.    USE - The method is useful for the preparation of a three-dimensional graphene/tungsten-based nanosheet/magnesium-doped zinc oxide layer-by-layer assembly structure, which is useful for sewage treatment, photolysis of water, air purification, and solar cells and for the separation of photo-induced electrons and electron-hole pairs in comparison with a homogeneous material.    ADVANTAGE - The method enables large-scale production of three-dimensional graphene/tungsten-based nanosheet/magnesium-doped zinc oxide layer-by-layer assembly structure in a simple and easy manner with high synergistic effect and improved photocatalytic performance.    DETAILED DESCRIPTION - The preparation method of a three-dimensional graphene/tungsten-based nanosheet/magnesium-doped zinc oxide layer-by-layer assembly structure, involves adding 1-10 g tungsten powder and 0.1-1 g cetyltrimethylammonium bromide to 500-1000 ml deionized water, performing ultrasonic dispersion for 20-40 minutes, stirring for 20-40 minutes to obtain tungsten-based dispersion liquid, shearing the tungsten-based dispersion liquid using mechanical shearing machine under ultrasonic oscillation at a rotation speed of 1000-8000 rpm for 1-3 hours, centrifuging the dispersion liquid at a rotation speed of 4000-8000 rpm for 1-3 hours to obtain tungsten nanochip solution, adding 5-15 ml graphene solution with concentration of 0.8-1.2 g/l to 30-70 ml deionized water, ultrasonically dispersing for 20-40 minutes to obtain graphene dispersion (1), adding 0.1-0.3 g anionic surfactant to the graphene dispersion (1) and then ultrasonically dispersing for 20-40 minutes to obtain graphene dispersion (2), slowly adding 1-5 ml tungsten nanochip solution to graphene dispersion (2) under stirring and ultrasonic vibration condition to obtain graphene/tungsten nanosheet composite dispersion solution, slowly adding 2.2-5.5 g zinc acetate and 0.24-0.96 g magnesium acetate to 50-100 ml deionized water and completely dissolving to obtain graphene/tungsten nanochip dispersed solution, ultrasonically dispersing for 15-30 minutes, transferring to water bath at a constant temperature of 60-90 degrees C, dripping 50-100 ml aqueous solution of oxalic acid having a concentration of 1-2 mole/l under constant stirring when the temperature is stable to form colloid, placing the colloid in an oven and then drying at 70-90 degrees C, grinding to obtain three-dimensional graphene/tungsten based nanosheet/magnesium oxalate precursor powder, placing the precursor powder in a box oven under nitrogen atmosphere, calcining at 400-600 degrees C for 1-3 hours, and naturally cooling.