Stimuli-responsive materials with wettability reversal have significant potential for controllable oil/water separation. Herein, an ammonia-responsive cotton fabric membrane was designed by a facile dip-coating approach. The cotton fabric membrane coated with nickel stearate particles presents superhydrophobic and superoleophilic. Interestingly, the membrane turns into superhydrophilic and underwater superoleophobic upon exposure to ammonia vapor. Accordingly, the as-prepared membrane can achieve controllable immiscible oil/water separation with favorable separating efficiency. More importantly, we found it was capable to effectively separate both water-in-oil and oil-in-water emulsions with promising flux and antifouling performance. Furthermore, the fabricating strategy is simple and the raw materials used in the production are not only economic but also environmentally safe, which will provide positive guidance in practical applications.