Abstract: The performance of underwater non-dispersion concrete admixed with polyacrylate and polysaccharides respectively are compared. It is shown that the shortcomings of concrete admixed with polyacrylate are basically overcome by substituting polysaccharides for polyacrylate. Afer blended 75s, there are no slump loss occurrence with 2h under dynamic or static states. The ratios of compressive strength cast in water and in the air exceed 85%. Cement of 400~800kg/m3 concrete would meet the needs of concrete with compressive strength of 20~30 MPa.