Recently, Carbon Fiber Reinforced Plastic (CFRP) composites are applied to the aircraft structure and also the pressure equipment such as pressure vessels and pressure pipes, etc. In particular, CFRP composites used in the aircraft structure are exposed to a low temperature environment at high altitudes. Nevertheless, there is not enough opened public data of CFRP composite material for the fatigue strength properties under various environments including low temperature below 0℃. In addition, it is useful to investigate also the influence of sea water absorption characteristics of the CFRP composites on the strength properties since CFRP composites are expected its high corrosion resistance.<br>In this study, we conducted static tensile test and fatigue strength test at a low temperature of −54℃ by using specimens with a circular hole made of CFRP laminate composite plate soaked in artificial sea water enough and also carried out observation of the fatigue damage progression in the low and room temperature environments. That is, we have investigated the following strength properties of CFRP laminate composite, ⑴ the influence of artificial sea water absorption on the tensile strength at low temperature −54℃, ⑵ the fatigue strength of the specimens absorbing artificial sea water at low temperature −54℃, ⑶ the fatigue damage progression behavior observed with soft X−ray inspection.<br>From these test results, we have obtained the basic data of CFRP laminate composite to be utilized to various large-scale structures.