Recent research developments on mechanical behaviours of 3D woven composites are reviewed. It is shown that the mechanical properties of 3D woven composites depend not only on the respective properties of the constituent fiber and matrix but also on the goemetric structure of the 3D reinforcement. The relationship between mechanical properties of 3D woven composite and micro-structure of the reinforcement is discussed, especially the geometric pattern of the filament bundle and the shape of its cross section within the 3D reinforcement, which play an important role in determining the performance of the woven composites. Experiment investigations concentrate on the observations and analyses of the damage mode of 3D woven composite and the effects of the 3D reinforcement in preventing the propagation of micro-cracks inside the material. Modeling techniques are applied successively, based on the lamina theory, average orientation model and finite element analysis, to investigate the elastic properties of 3D woven composite. However, further work is still required before the strength and damage of the 3D woven composites can be properly predicted. Some suggestions for further investigations are also made in this paper.