Blast-furnace slag cement (BB) is made by mixing granulated blast-furnace slag into Ordinary Portland cement (N). Slag cement concrete has been intensively studied because of its ability to get improved durability. However, in order to get high durability of slag ccmcnt concrete, enough wet curing condition and curing period is necessary. At present technical situation, there are not enough unified techniques to evaluate the chloride ion diffusion properity of slag cement concrete quantitatively. And the relation between various test methods and the chloride ion diffusion coefficient is also not examined thoroughly. In this study, by converting the substitution rate of slag and by changing its curing condition, compressive strength of the BB, not curcd in moisture was much lower than the other cured in wet condition. While, in longer moisture curing it can get the same strength as the N. From the results of both electro-migration test and submergence in salt water test, the higher the substitution rate of slag and the longer the moist curing period is, the smaller the diffusion coefficient is. And the influence level of cumulative pore volume on chloride diffusion property is different between N and BB.