Recently there has been a large growth of research effort for nanoelectronic devices.Investigations of quantumly coherent nano-meter scale systems whose fabrication has been made possible by recent advances in experimental and sample preparation techniques have revealed that transport properties could be non-Ohmic and G could be quantized. Understanding electron conduction in such devices is an extremely active research topic. Our theoretical goal is to predict quantum transport properties of molecular nanodevices including their I-V characteristics from first principle theoretical method.