The invention provides a pretreatment device for uranium dioxide raw materials for MOX. A drying box is connected with a gas drying and dedusting device. The gas drying and dedusting device is connected with a mechanical pump. The mechanical pump is connected with a one-way valve, and the one-way valve is connected with an electromagnetic valve A. The electromagnetic valve A is connected with thedrying box. Both the one-way valve and the electromagnetic valve A are connected with an electromagnetic valve B and an electromagnetic valve C. The one-way valve can be opened only in the direction from the mechanical pump to the electromagnetic valve A.