Based on the double-K model,the effect of seawater curing and seawater agitation on the fracture properties of concrete was studied by three-point bending test in this paper. The test results show that:Seawater mixing reduces significantly the initiation load and peak load of concrete,and also reduces the initiation fracture toughness and instability fracture toughness of concrete. The maxima of decreasingare 52.6% and 25.6% respectively. The effect of seawater maintenance on the fracture parameters of double-K is relatively small,and the ranges of fracture toughness and instability toughness are 3.2%~23.4% and 12.7%~20.8%,respectively. In addition,under the influence of seawater,the calculated fracture energy is obviously reduced,and the range of decrease is 14.5%~28.1%.The effect of seawater on the compressive strength of concrete cubes is fairly minor.