: The global supply of energy is highly dependent on fossil fuels and gives rise to global warming due to the emission of greenhouse gases such as carbon dioxide. Fuel cells are emerging technologies for clean power generation in place of the combustion of fossil fuels. Particularly, polymer electrolyte membrane fuel cells (PEMFCs) can be used as alternatives to internal-combustion engines in vehicles, as well as power supplies in stationary and portable applications. Furthermore, for PEMFC-based applications to achieve commercial success, the membrane must be capable of performing well under increasingly stringent operating conditions (e.g., high temperature, low relative humidity). Even Nafion, currently the most widely used membrane, does not satisfactorily meet all of these criteria. Sulfonated polyimides (SPI) have been considered as promising alternative for Nafion. Sulfonated polyimide has good properties but suffers from hydrolytic stability. Researchers have suggested different routes to increase hydrolytic stability of polyimide. Using aliphatic moeties in polymer structure is one of important route to increase hydrolytic stabilityin polyimide. In this project, three kind of aliphatic-ether diamine like: 1,13-diamno-4,7,10-trioxatridecane (TOTD), 4,9-dioxa-1,12-dodecane diamine (DODD) and 1,8-diamino-3,6-dioxaoctane (DOO) be used. Also, 3,3?,4,4?-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4?-oxydianiline (ODA) as fully aromatic dianhydride and diamine, has been used. Post-sulfonation was applied for sulfonation of polyimide. At first step polyamic acid prepared from diamine and dianhydride and then Polyamic acid treated with concentrated sulfuric acid for two hours for carring out post-sulfonation method. Then, sulfonated polyimide membrane was prepared by thermal imidization of casted film. This project based on two parts. At the first of the project, four membranes prepared. Because two of the membranes were broken. The characteristic parameters of the membranes were not measured. Fully aromatic SPI membrane and SPI membrane contain 20% DOO diamine successfully prepared and characterized. Water uptake result showed that both membranes could absorb 5.4% water while is lower than Nafion. But average number of water molecules per sulfonic acid group (?) is higher than Nafion. Hydrolytic stability for SPI contains 20% mole aliphatic-ether moiety was measured about 60 hours and it was 48 hours for fully aromatic structure. Ion exchange capacity (IEC) for fully aromatic structure was 0.379 equiv/gram and it was higher than SPI contain 20% mole aliphatic-ether moieties but both of them have lower IEC than Nafion. Proton conductivity increased from 1.5 × 10 -3 (mZ/cm) for SPI contain 20% mole aliphatic-ether moieties to 2 × 10 -3 for fully aromatic SPI, measured proton conductivity for Nafion was 10 -4 . So both synthesis membranes had higher conductivity than Nafion. At second part of project nanocomposite membrane prepared by addition nano silica to fully aromatic SPI at various weight percentage. Micrograph photo observation indicated phase separation between Ionic and non-Ionic sequence. IEC for nanocomposite membranes contain 2, 4 and 8 wt % was respectively, 0.316, 0.242 and 0.081 and proton conductivity was 10 -2 , 2.2 ×10 -3 and 6.1 ×10 -2 . Proton conductivity of nanocomposite membrane was higher than pristine SPI and Nafion. Maximum measured water uptake was 11% for nanocomposite membranes contain 4 wt% nano silica. Generally, addition nano silica to sulfonated polyimide increased water uptake and ? than pristine SPI. Keyword: sulfonated polyimide, post-sulfonation, aliphatic-ethric diamine, sulfonated polyimide-nano silica nanocomposite, thermal imidization.