Oxidization of diamond in the sintering process of diamond/glass composites results in uncontrolled expansion with many irregular pores and low bending strength of the tools. In this paper, Al powder was used as oxygen getter due to its excellent affinity with oxygen. Its oxidization product, Al2O3, entered into glass network. Consequently, oxidization of the grits was inhibited, and the wettability of diamond grits by the matrix improved. As a result, the expansion phenomenon was inhibited and the bending strength improved for all the composites. The minimum volume expansion rate and maximum bending strength were obtained for the composite with 4 wt% Al powder. This Al content resulted in a decrease of volume expansion rate from 175.2% to −10.9%, and an increase in bending strength from 11.3 to 75.1 MPa compared with the composite without Al powder.