In order to obtain reasonable mix ratio of coastal tunnel lining concrete and improve selfwaterproof performance of concrete，taking the Gongbei Tunnel project as background, the selfwaterproof performance study of concrete in the coastal erosion environment is carried out. The preliminary mix ratio of the waterproof concrete is determined based on systematic concrete mix ratio design method. The influence of the coastal environment on the selfwaterproofing performance of concrete is simulated by carbonation and sulfate erosion laboratory test. Through the test analysis of concrete compressive strength, water resistance and chloride ion resistance, the optimal mixture ratio is obtained. The result shows that: (1)The concrete with 20% fly ash and 10% slag has the best selfwaterproof performance, which can be used as the main structure of Gongbei Tunnel. (2)Under the carbonation and sulfate erosion, the chloride ion resistance of concrete decreases with time and its compressive strength increases. (3)The strengthening effect of concrete admixtures on chloride ion resistance is very obvious, but it has certain influence on the increase of concrete strength in later period.