Vacuum infiltration is one of the composite production method. Reinforcement volume ratio, vacuum value, molten matrix composition and temperature, infiltration atmosphere and time are important parameters in infiltration of molten metal into preformed reinforcement. In this study, MgO powder and Al were used as reinforcement and matrix respectively. Mixture of MgO and Al powders with -105 mu n particle size were filled in quartz tubes freely to form 30 % reinforcement volume ratio. Liquid pure Al with varying Mg contents were vacuum infiltrated into the MgO powder under 550 mmHg vacuum at two different temperatures in normal atmosphere for 3 min. After vacuuming, infiltration height and density of produced composite have been determined. Fracture behavior of composites has also been determined by three point fracture test. Microstructure of composites and fracture surface were investigated by SEM analysis. It has been found that fracture strength of composites decreased although infiltration height and density increased with increasing Mg content of liquid Al. It has been also determined that molten metal temperature facilitates infiltration.