Energy-dispersive X-ray spectroscopy (EDS) is widely used for element analysis which identifies constituent elements in a specimen. Recently, performance of elemental analysis with EDS has been improved by using large-sized silicon drift detectors (SDDs) and atomic resolution EDS mapping were obtained by using Cs corrected-STEM.We developed ultra-high sensitive Dual EDS system which has two 100mm2 sensor silicon drift detectors (SDD1 and SDD2) and optimized ultra-wide gap pole piece for maximum solid angle and take-off angle. The SDD2 is placed in the direction of the sample holder rod and is located at a closer position to the specimen than SDD1, because the special specimen holder has a shorter length in the holder rod direction. These components were integrated in newly 300kV aberration corrected microscope (GRAND ARM). The calculated solid angle and take off angle of each SDD become as following number, SDD1 (0.55sr, 25 degree) and SDD2 (1.08 sr, 29 degree).We investigated sensitivity of this system by using EDS peak intensity of Ni-K obtained from a Ni thin foil. The intensity of the SDD2 is approximately 1.9 times larger than that of SDD1 due to the shorter distance between the detector (SDD2) and a specimen. The solid angle of SDD2 is about two times larger than that of SDD1, which correspond well to the intensity difference of the Ni-K spectra. We also investigated performance of atomic resolution EDS mapping obtained from SrTiO3 single crystal. Sr and Ti columns distribution were clearly visualized. at a short acquisition time of 157 s (number of pixels = 256×256). This proves a high analytical efficiency of the present system. It is clear from the short acquisition time of this system that the dual SDD system is very powerful tool for elemental analysis of damage-susceptible materials such as latest materials.