Diamond wire sawing has been used for many applications in stone industries and civil engineering several decades ago. The wear of bead is a major factor that affects wire-sawing performance in machining process. In this paper, seven diamond wires with different matrix system and different structures are taken from the factory. The diameters in the front, middle and end of bead along the moving direction of diamond wire, are measured respectively. The wear of diamond grits is also observed using a digital video microscope system. It is show that the wear of bead varies along the moving direction of diamond wire. The wear in the front of bead is greater than the others. The diameter gaps are associated with the type of matrix and the wear of diamond grits. The diameter gaps keep constant in the smooth sawing process.