Abstract: Based on representative concrete design mixes used in the domestic railway project,the concrete's chloride-ion penetration is studied and its influencing factors are also analyzed.Results show that concrete curing age,type,and volume of mineral admixtures are the main influencing factors of concrete's chloride ion penetration.With the concrete curing age extending,the chloride-ion penetration value lowers and it is reasonable to evaluate test results through curing age of 56 days.Adding the volume of fly ash and ground granulated blast furnace slag(GGBS),the chloride-ion penetration value declines.The effect of reducing concrete's chloride ion penetration of fly ash is much better than that of GGBS,and both effects are almost equal when the volume reaches 40%.Other concrete mixed parameters,such as water binder ratio,air content,and types of cement and super plasticizers are less important influencing factors.