A novel quaternary ammonium cationic surfactant (N-octadecyl-N, N’-dimethyl-ethane-1, 2-diamine, C18DEDAM) was synthesized by 2-Chloroethylamine hydrochloride and Octadecyl dimethyl amine (C18DAM) at 70oC for 7h under the condition that the pH value was 7, and the compound structure was confirmed by IR and 1HNMR. The cmc was measured by conductivity measurement, and the cmc value is 4.6?0-3mol/L. C18DEDAM can form wormlike micelles as the NaSal concentration is 1 wt%. The shearing test shows that C18DEDAM-NaSal system has the shearing thinning ability that is the characteristic of wormlike micelles, and the viscoelastic test indicates that the system shows the characteristic of gel. Besides the surfactant can achieve high viscosity in acid condition, which indicate it is one kind of smart viscoelastic surfactant.