Nanotechnology is the linkage of Metallurgy, chemistry, physics science and engineering to provide methods and processes for production and assembly of useful structures and preparation and production of materials and devices which are at least in one of their dimensions of nano-scale (10 -9 -10 -7 ). Nanocomposites are strong replacements for filled polymers (containing fillers) or ordinary blend polymers. Precipitated calcium carbonate as filler in paper industry, paint, drug and plastics has been used. Using calcium carbonate nanoparticles instead of traditional particles shows apparent changes in container materials. So lots of researches have been done on its preparation and production methods. In this work, after introducing the most applicable production methods, we have presented a new method based microemulsion method for the synthesis of calcium carbonate nanoparticles. In formation of microemulsions a mixture of Span ® 80 and Tween ® 80 surfactants instead of just one of surfactants was used and the effect of surfactant value on the size of synthesized nanoparticles was investigated too. Using XRD, the mean size of particles was estimated around 38 nm. According to comparison of effect of synthesized nanoparticles on physical- mechanical properties of polymeric nanocomposites and traditional composites, first the surface of calcium carbonate nanoparticles and micron size calcium carbonate particles was treated using solution of stearic acid in toluene in boiling point of toluene for 1h. Then using synthesized calcium carbonate nanoparticles and micron size calcium carbonate particles too, as filler in polymeric matrix of polyamide 66, nano and traditional composites were prepared. Finally tensile properties of the both of nano and traditional composites where investigated. Results of experimentals show enhances in the tensile properties of both kinds of composites. In comparison with elasticity module of non reinforced polyamide 66, in weight fraction of 2.5%, 5% and 10%, elastic modulus of nanocomposites increased 9.2%, 22.4% and 33.5% respectively, while elastic modulus of traditional composites increased 2.3%, 11.7% and 20.3% respectively. In order to prediction of elastic modulus theoretically for comprising with experimental data, rule of mixture, Guth, Nicolais - Narkis, hashin and halpin-Tsai equations were used. Results show that use of theoretical models for prediction of elastic modulus is not very consistent for particulate nanocomposites. However these models can be used to prediction of elastic modulus surely, because experimental data are upper than theoretical data.