During the two years of 2001 and 2002, field experiments and simulating trials were conducted to study hydrosalinity balance on different type of coastal soils(respectively situated in Laizhou region of Shandong province, Dafen region of Jiangsu province, and Yuedong region of Hainan province) under seawater irrigation. The results showed that, irrigated with suitable amounts of blended water with different salinity level, the soil profile in Laizhou had a trend to accumulate soluble salts, but when using the blended water with salinity level of 20 ds/m, total salt in 0~60 cm soil layer was also less than 0.3%. In Dafen region and Yuedong region, respectively irrigated with blended water of 24 ds/m and 30 ds/m, total salt in 1 m soil mass obtained hydrosalinity balance. In semiarid region of Laizhou, total salt in 0~60 cm soil layer fluctuated a bit, implicated that evaporation played a dominant role in salt and water movements. While in humid region of Dafen, total salt below the 30cm of soil layer maintained rather stable, which indicated that stable ground water table mainly influenced salt and water movements. In the experiments of seawater irrigation, the result also showed that total salt in upper soil layers was less than that in deeper soil layers in varying treatments during the summer. In the study of water-contained characteristics of the coastal saline soils, we found that seawater irrigation could reduce soil suction, that is, seawater irrigation could render the soil keep more water for plant utilization, especially for halophytes.