Abstract: The tensile failure behaviours of six multi-ply carbon/epoxy composites （[0/90]s, [±45]s, [30/60] and three kinds of carbon cloths） have been investigated. Acoustic emission technique was employed in monitoring their damage process together with microscopical observation.The occurrence of acoustic emission weighted ringdown signals indicate the release of strain energy at the initial damage of the composite materials. Generally, for [±45]s, [30/60] ply and transverse carbon cloths specimens whose stress-strain curves all have an inflection, initial damage acoustic emission signals occur al this location, for most of them in the vicinity of 40% ultimate strength and maximum strain. Their maximum weighted ringdown counts are of the same order of magnitude, but their total A. E. weighted ringdown counts differ magnificantly. This shows that the total energy of damage released is quite different for the differently plied composites. Due to deformation and damage, the A. E. pattern of the carbon cloth specimen demonstrates continuous energy release, but that of bidirectionally plied specimen shows discontinuity. The A. E. signals of cross-ply specimen occur at regular intervals with little change in the amplitudes of the weighted ringdown signals. This indicates homogeneous orthotropy for [0/90]s specimens. However, for [±45]sand [30/60] specimens energy release is concentrated at the final stage.