Abstract: The deep-sea environment was simulated through pressure vessels with nitrogen pressing system, and the seawater absorption data of glass fiber reinforced epoxy resin composite (GF/CYD-128) laminates under different pressures was obtained by weighing method to investigate the seawater absorption behavior of GF/CYD-128 laminates in the deep sea environment. The results show that the saturated seawater absorption of GF/CYD-128 laminates firstly decreases with the seawater pressure then increases with the increasing pressure. The saturated seawater absorption of GF/CYD-128 laminates deceases to the minimum value at the pressure of 2.5 MPa. The relationship between the saturated seawater absorption and the seawater pressure can be depicted by the quadratic polynomials. The seawater absorption behavior of GF/CYD-128 laminates at the deep-sea enviroment is non-Fick, however, it can be simulated by the Langmuir-type model. The seawater absorption behavior of GF/CYD-128 laminates under the deep-sea pressure is successfully predicted by the Langmuir-type model.