Current research was performed in two steps. In the first step, in order to characterization of powder obtained from RTV Polymer pyrolysis, first amount of 1 Wt% hardener was added to 30 gr of polymer and then was heated from room temperature to 700?C and was kept in this temperature for 30 minutes. After completing of pyrolysis process, the product of reaction was investigated with Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR), and its specific surface was investigated by BET method. According to obtained results, material was SiO 2 nanoparticles with amorphous structure and with 220 m 2 /g specific area. In the second step, Aluminum matrix nanocomposite was produced by stir casting with in-situ method and via pyrolysis of RTV organic polymer in melt. In order to improve wettability, 2% magnesium was added to matrix alloy. In this step, effect of addition of RTV polymer to melt in amount of 1, 2, 3, 4% on the structure and mechanical properties was studied. Microstructure investigations, showed presence of a suitable bond between reinforce particles and matrix. The results of mechanical analysis showed 46% increase in hardness for A3 sample rather to instance sample. For this sample, shear strength, yield strength and Ultimate strength rather to instance sample, was increased to 52.7, 37.1 and 39.3% respectively. Key words: Aluminum matrix nanocomposite, pyrolysis of RTV organic polymer, in situ method, stir
