Metal Matrix Composite is a metal composite that utilizes an aluminum alloy as a matrix in its fabrication and has a wide application in industry. Process of making specimens using an amplifier the powder metallurgy method. Fly ash as reinforcement was varied in powder mixing by 5%, 10%, 15%, 20%, and 25%. The compaction process is carried out with hot isostatic pressure so that the powder becomes softer and makes it easier to compact. Effect of heating temperature on the mold varied at 250^oC, 300^oC, and 350^oC to obtain a homogeneous bond. In the research conducted, the results showed that the hardness value of the specimen increased by 1.7% by 65.07 HRB at 10% fly ash reinforcement variation, then continuously decreased to 16.92% with a hardness value of 55.64 HRB in the reinforcement variation. Fly ash 25%. The results of scanning electron microscope observations show that the influence of the heating mold provides an even distribution of particles at a temperature of 300^oC. At temperatures of 250^oC and 350^oC shows an uneven distribution of reinforcing particles and results in agglomeration of reinforcing particles in the specimens are The resulting product is brittle and causes a decrease in hardness in the variation of the fraction with fly ash content above 10%.