The present invention relates to a method of recovering mortar used in the wire cutting of monocrystalline silicon or polycrystalline silicon. Silicon is an important material for solar batteries, semiconductors, liquid crystal displays, etc. A silicon rod is cut into silicon wafers by the wire cutting technique, and in the process, a wire-cutting machine needs to be added with cutting liquid mortar, which is mainly composed of liquid phase polyethylene glycol and solid phase silicon carbide powder. When the wire-cutting machine cuts the silicon rod, the solid particles in the mortar are changed into waste mortar as the silicon carbide grinds the silicon rod and a steel wire. If the waste mortar is discharged directly, environment is polluted, and the raw material is wasted. The present invention adopts the mortar-recovering technique to recover the waste mortar, so that the waste mortar can be reused and the discharging of the three wastes can be reduced, so while reducing production cost, the mortar-recovering technique can protect environment. The technique of recovering mortar used in the wire cutting includes the following flow: waste mortar dope, one-step membrane filtration and PEG liquid; waste mortar dope, one-step membrane filtration, cleaning, powder drying, powder classification and SiC powder.