Abstract: By Using SEM,the morpholoth of coarse particle W powder and WC powder manufactured by blue tungsten and yellow tungsten as raw materials has been observed and a comparison between the microstructure of the corresponding WC-Co cemented carbide phases has been made. On such base,a common phenomenon of micropore in WC grain of cemented carbide has been explained. Namely,the micropore in WC in alloy was mainly yielded from raw material W powder. Experimental results show that choosing blue tungsten as raw materials to produce cemented carbide can obviously decrease the micropore in WC grain of cemented carbide. Therefore,the comprehensive properties of the alloy can be improved.