A method based on AC impedance technology using active porous silver as electrode is put forward for measuring the chloride ion diffusivity on surface layer of concrete. The results show that the proposed method exhibits good ability to distinguish the chloride ion diffusivity on surface layer of concrete with different binding materials. Besides, the method has features of non destructivity and short test time. The method can be used in in situ measurement for chloride ion diffusivity on surface layer of concrete, which can provide key data for durability assessment of concrete structures.