The invention discloses a solar-grade 
silicon wafer being 
cut by 
a diamond wire and a 
cutting method thereof. A mono-
crystalline silicon square rod is 
cut by 
a diamond wire. The 
cutting method comprises the following steps that: the mono-
crystalline silicon square rod which is formed by squaring, 
grinding and 
sharpening a mono-
crystalline silicon circular rod, the mono-crystalline 
silicon square rod is fixed on a resin strip through an 
adhesive bar, the resin strip is fixed on an 
adhesive plate, then the 
adhesive plate and the mono-crystalline 
silicon square rod are collectively placed into a working cabin to be preheated, 
cutting liquid is circulated in the working cabin to work, then the 
diamond cutting is performed, the 
cut mono-crystalline silicon 
wafer is inversely arranged on a degumming device to degum, and the mono-crystalline silicon 
wafer is washed by ultrasonic and then is centrifugally dehydrated. Due to the adoption of the cutting method, the 
photoelectric conversion efficiency and the cutting efficiency of the mono-crystalline silicon wafer can be improved, a silicon wafer with the thickness of 140 to 200 micrometers can be produced, the qualification rate of the product can reach more than 98 percent; and silicon 
powder is recyclable, so valuable silicon resource can be saved, and the environment-friendly production can be really realized during the production process.