Abstract: The longitudinal tensile and compressive experiments on 3D 4-directional braided carbon fiber/epoxy resin composites with three different braiding angles were performed in thermal environments. The effects of temperature on the longitudinal tensile and compressive properties of 3D braided composites were discussed. Macro fracture morphology and SEM micrographs were examined to understand the damage and failure mechanism. The results show that the longitudinal tensile strength of 3D 4-directional braided carbon fiber/epoxy resin composites goes up slightly and the longitudinal compressive strength decreases obviously with the increase of testing temperature. The braiding angle has no apparent impact on the longitudinal tensile failure characteristics of composites. However, the effect of braiding angle on the longitudinal compressive failure characteristics of composites is obvious. As the temperature increases, the damage and failure patterns of 3D braided composites with three different braiding angles are obviously different than in room.