▎ 摘　　要

NOVELTY - The device comprises a housing ( 11 ) and several sieving plates ( 12 ), and the several sieving plates are arranged in the housing. The housing is formed with several sieving cavities ( 13 ). Each sieving cavity is provided with a discharging port ( 14 ). The top layer of the sieving cavity is fixedly connected with a feeding port ( 15 ). Each of the different sieving plate are provided with different apertures. The materials with different grain diameters are filtered by different diameters. The material comprises graphene powder. USE - Multi-stage sieving device for use in graphene micro-sheet preparation system ( claimed ). ADVANTAGE - The multi-stage sieving device makes the powder with standard grain diameter in the crushing process can be discharged in time, and avoids the repeated crushing, the utilization efficiency of the energy is greatly improved. The two kinds of powder with different grain diameters obtained by processing raw material can be used for producing heat-conducting filler, finally realizing the full utilization of the graphene raw material, realizing the hundred percent recycling of the raw material. The multi-stage sieving device can obtain two products with different grains diameters. The material height of the vacuum suction pump suction direction or/and the output direction controls the suction rate of the pump, so that the material height is in the set range. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: 1. graphene micro-sheet preparation system; and 2. a method for preparing graphene micro-sheet by using the graphene micro-sheet preparation system. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the multi-stage sieving device for use in graphene micro-sheet preparation system. Hosuing (11) Seive plate (12) Sieve cavity (13) Discharging port (14) Feeding port (15)