Effects of underwater antiwashout admixture(AWA), high-range water-reducing admixture(HWRA), defoamer(DF) and silica fume(SF) etc. on the washout resistance and com- pressive strength of concrete were investigated, and kinds of durability indexes for two typical underwater antiwashout concretes(UAC) were compared with normal concrete of the same strength grade. The results indicate that, (1) water demand of concrete increases and compre- ssive strength decreases with the increase of AWA dosage; (2) when HWRA and AWA are added together, there is an optimal HWRA dosage for obtaining good concrete properties; (3) adding DF and SF has the advantage in improving the workability and compressive strength of UAC; (4) the durability indexes such as impermeability, freeze-thaw cycling resistance, chemical attack resistance, carbonation resistance and Cl~- impermeability etc. of UAC all exceed that of normal concrete with the same strength grade.