Investigations in field of composite and nano-composite fabrication have significantly grown in past few years. In relation to elastic behavior of nanocomposite, many research have been done. This thesis is aimed at investigating thermoelastic behavior of aluminuim based nanocomposite reinforced by silicium carbide nanoparticle affected by thermalshock in transient heat transfer. In case of improving thermoelastic propertie SIC can be applied. Reinforcement efficacy depends on several parameters such as shape, reinforcements direction, reinforcements distribution, size and volume percentage. This nanocomposite is reinforced by spherical nanoparticles. Determining the effect of Diameter and volume percentage of nanoparticles is the aim of this thesis. Therfore simulatio by finite element method has been done by applying the ABAQUS software. This simulatio is done by Phytonm programming and representative volume element have been applied to reduce cost of calcuations. In this simulation Nanoparticles are randomly distributed in metal matrix. At first simulation of simple tensile test i applied to RVE and the result is verified by articles. After applying, boundry conditions of thermal shock to RVE in transient heat transfer and resulted temperature variation and thermal stress will be observed. All these processes (simulation and changing data to information) are programed and performed by computer. After all evaluations we came to conclusion that as lonh as nano particle’s diameter increases, the thermal stresses will be decreased. For example by thermal shoke exertion, the average thermal stress by 80 nm to 100 nm change in diameter, will face 40 percents decrease. The point in case of changes in thermal stresses, at the end of exertion is that the nanocomposite face 31 and 47 percents decrease for nano particles with 80nm to 120 nm diameter. Finally it worthes mentioning that temperature and thermal stresses along with diameter changes from 80 nm to 100 nm are bigger than changes from 100nm to 200 nm. Keywords: Nanocomposite, Thermoealastic behavior, Dimeter and volume percentage of nanoparticles, Transiant heat transfer, Phyton, Finite elemant method, Representative volume element