Long-term acid-resistant mordenite membranes are prepared on the porous mullite supports by secondary hydrothermal synthesis in this study. Influences of the preparation conditions (fluoride, synthesis time, molar composition of precursor synthesis gel, and alkaline of the precursor synthesis gel) on the growth and pervaporation performance of the mordenite crystals and membranes are studied in detail. The fluorides containing the precursor gel could improve the acid stability and hydrophilicity of the mordenite membrane greatly. The Si/Al ratio, separation performance, and mordenite crystals morphology of the mordenite membranes depend on the Si/Al ratio of the initial synthesis gels, and medium alkalinity is crucial to prepare the compactness mordenite membrane layer by OH- and F- as mineral agents. As the molar ratio of the initial synthesis gel is SiO2:0.01KF:0.08Al(2)O(3):0.2Na(2)O:35H(2)O, the mordenite membranes have good dehydration performance and reproducibility for dehydrating a 90 wt % acetic acid/water mixture. The well reproducible mordenite membranes have long-term stable dehydration performance for continuously dehydrating a 90 wt % acetic acid/water mixture by pervaporation. When the post-treatment temperature is lower than 100 degrees C, the mordenite membranes still keep their integrity after immersion in a 95 wt % acetic acid/water aqueous mixture for 48 h.