A new H3O+ ions containing air stable complex [Fe-II(CN)(6)][(CH3)(4)N](2)(H3O)(2) (1) with fish-net like {[Fe-II(CN)(6)](H3O)(2)}(2-) anions and fish like tetramethylammonium cations is obtained. The crystal structure and magnetic properties have been characterized. The study of the magnetism reveals that the typical diamagnetism of low spin (LS) Fe-II. The presence of H3O+ ions prevents Fe-II ions from oxidation in the system, which is proved by DFT investigation and offering a handy approach to obtain the stable Fe-II ion containing material hard to prepare previously. The hydrogen bonding network might be interesting to the proton conductivity research, as well.