Application of energy filtered transmission electron microscopy (EFTEM) to nano-scaled precipitates in aluminum alloys were investigated to know their chemical compositions. Its resolution, which can confirm the existence of elements, were also reported and compared with theoretical ones. In Al-15 mass% Ag and A1-4.0 mass% Cu Al-Cu alloy, G.P. zones in both alloys were observed and confirmed G.P. zones larger than 3.4 and 1.6 nm, respectively. We have also applied this technique for the beta 'phase in Al-1.0 mass% Mg2Si alloy and the GPB zone in A1-4.3 mass% Cu-1.8 mass% Mg alloy. It finds that it can be observed elemental maps when the beta ' phase in Al-Mg-Si alloy is larger than 4.7 nm (Mg-map) and 4.2 nm (Si-map). In the case of GPB zone in Al-Cu-Mg alloy, it can be observed larger than 2.1 nm (for both of Cu and Mg-map).