The purpose of this work is to analyze the damage process resulting from buckling load applied on composites reinforced by flax fibre. Continous buckling test was performed on specimens until cracks appeared on their outer face. This test was monitored with an acoustic emission system. The high sensitivity of this method allows the detection of any process or mechanism generating sound waves. Moreover, this technic has the advantage of not causing contact in the deformed zone and thus to overcome the parasitic damage that may result from the stress concentrations in these areas. A multiparametric analysis is used to identify the acoustic signatures corresponding to each damage mechanism involved in the materials, and then follow their evolution in order to identify the most critical mechanisms leading to the final breakage of the material. The presence of these damage mechanisms was confirmed post-test by microscopic observations. Three orientations of laminate specimens (0°, 90° and 45°), relative to flax fabric architecture, were tested in order to characterize and highlight on their own damage process. Similarities as differences were observed between these mechanisms. We have deduced that the high porosity rate found in our composites are resulting from manufacturing parameters. Architecture and properties of the flax fabric influenced negatively the mechanical properties later by accentuating the gap between theoretical and practical values (17% to 22.4%) and by accelerating the development of certain damages such as matrix cracking which acoustic hit density is superior to 70% and fiber/matrix decohesion which occurs very early.