Multi-stage screening machine

The utility model discloses a multi-stage screening machine. The multi-stage screening machine comprises screening units; the multi-stage screening machine comprises N stages of screening units, and a conveyor used for conveying materials which flow out of a back material discharge hole of each stage of the screening unit back to a material feeding chamber of the last-stage or first-stage screening unit; a front material discharge hole of the last-stage screening unit of the screening units is connected with a material charge hole of the next-stage screening unit, wherein N is a positive integer greater than or equal to 2. According to the multi-stage screening machine, a single screening machine in the prior art serves as the screening unit; a plurality of screening units form the multi-stage screening machine through an ingenious design, and the materials are screened repeatedly, so that the screening effect of fine hair is remarkably improved; the multi-stage screening machine has the advantages of low lab