The composites of mechanical and thermal properties of modified and unmodified Carbon nanotube/epoxy resin nanocomposites tested under various circumstances is a major investigation in this study. Identification of functional groups of CNT surface using Fourier transforms infrared spectroscopy (FTIR) was done to male sure if the means of modification adopted in this study is successfully. The tensile and flexural strengths of modified CNT-containing nanocomposites with the amount of modified CNT around 0.75 Phr tested under room temperature circumstance increase 10.96 % and 21.44 % respectively. These two strengths of nanocomposites tested under high temperature circumstance increase 14.55 % and 10.80 % respectively. Additionally, both strengths of nanocomposites tested under high temp.-high humidity circumstance increase 11.65 % and 23.53 % respectively. According to the test results using pyris diamond thermomechanical analyzer (TMA) coefficient decreases 39.81 % with increasing the content of modified CNT and meanwhile glass transition temperature increases 4.15 %. Because of above-mentioned effect, a modified CNs-containing nanocomposite possesses great thermo stability. Overall, No matter what circumstance (high temperature or high temp.-high humidity circumstances) nanocomposites expose to, and no matter whether CNT are modified or not, CNT do significantly enhance mechanical and physical properties of composite. © (2010) Trans Tech Publications.