Influence of pH value of emulsified asphalt on work performance of CA mortar was studied by measuring the effect of pH on zeta potential. Results show that the pH of emulsified asphalt has great influence on the fluidity, working time, separating degree, air content and apparent density and pH of CA mortar, which results in the influence of pH of emulsified asphalt on zeta potential. When pH=2.59.5, the fluidity of CA mortar keeps in a stable level, while pH＜2.5, the fluidity increases, and it increases significantly when pH＞9.5, the fluidity reaches a maximum value when pH=11.5.The loss of fluidity with time reaches to 26.09% when pH=9.5.The apparent density decreases with time when pH =2.5, and it increases when pH=9.5. Separating degree has no effect on the symbols of the ζ potential, but it has influence on its absolute value. The bigger the absolute value, the smaller the separating degree and vice versa. When pH=1.5 and 9.5, the separating degree was small. pH of asphalt has a little influence on the pH of CA mortar. The appropriate pH of asphalt for CA mortar is 1.5 or 9.5.