The effects of alkaline cations (M+ = Li+, Na+, K+, Cs+) on the electrochemical synthesis of polyaniline were cartied out under cyclovoltammetric conditions using nitrates of Li+, Na+, K+, and Cs+ as the supporting electrolytes. The results show that the oxidation potentials of aniline in the electrolytes decrease as the protonation extent of aniline decreases from the first scan, which is caused by the decrease of the ionic radius of alkaline metal ions at the same concentration of alkaline cations. With the scan number increasing, the deposit charge Q as the characteristic growth function also depends on the protonation of aniline, and it increases with the ionic radius of alkaline cations increasing. SEM images show the effect of alkaline cations on the morphology of polyaniline. It is clear that the ionic mobility of alkaline cations is further lower than that of H+. Alkaline cations and counter-ions were the species responsible for the enhancement of Pani electrosynthesis. Therefore, this is exactly what SEM images show: a relatively rough fibrous structure in the case of Pani-H+ suggesting a sponge-like structure and a highly orderly fiber-like structure in the case of Pani-M+.