In order to investigate the influence of different porosity carbon fiber/epoxy resin laminates on the bending mechanical properties at the high and low temperature and hygrothermal aging environment and subjected external load, the supersonic state and the internal stress state were simulated. High and low temperature accelerated hygrothermal cyclical tests for T700CF / 3234EP were employed to simulate supersonic aircraft service environment. Three laminates with porosity of 0.04, 0.08 and 0.11 were prepared by controlling the molding pressure. The loading of the laminates was loaded with 0, 30%, 40% and 60% of the maximum bending load of the laminates, respectively, and then placed in the high and low temperature environment test chamber. The bending strength of composite laminates under different temperature cycles is measured respectively, which were simulated based on ABAQUS software. The experimental results show that the external load and porosity increase the bending strength reduction of the laminates under the alternating temperature and humidity field.During the high and low temperature and hygrothermal cycle 4~6 periods, the secondary curing phenomenon becomes more obvious as the load increases andthe changes of the bending strength of the laminate is relatively gentle. The calculated trend of bending strength based on finite element model was consistent with the experimental results. The effects of high and low temperature, hygrothermal aging environment and external loading on the bending strength of composites were explained. The bending property of carbon fiber / epoxy resin laminates with different porosities were predicted accurately.