Mineral admixtures, such as slag, fly ash, and natural pozzolans, have been used in the concrete mix proportions to improve the durability of concrete. The fundamental properties of high-volume fly ash concrete were investigated in order to use fly ash more actively as an industrial by-products. The purpose of this study is to evaluate chloride attack resistibility of concrete mixed with fly ash. In this paper I would like to examine chloride attack resistibility of concrete mixed with fly ash using migration test, and to reliability approach to service-life prediction of concrete exposed to marine environments. The results of this experiments are summarized as follows ; 1) The chloride ion migration coefficients of concrete mixed with fly ash were evaluated using migration test, NT BUILD 492 method, quantitatively. 2) The chloride attack resistibility of concrete was improved seriously by mixing with fly in normal strength concrete.