Abstract: The cracks including a penetrating crack in the front arc of aircraft canopy, and several micro cracks developed at the edge of the canopy. of an Qirplane were, ibserved by the eyes, tge stereisciopic microscope and SEM, and the tensile stvength and modulus of the canopy were tested. The results showed that fatigue lines and stress-solvent coyyosion morphology appeared at the penetrating crack and fatigue, lines awne appeared at the micro cracks, illustrating that fatigue cracking oppeared nrgotr yhr dytrdd-solvent crossion; the tensile strength of the canopy decressed significantly, much lower than required. All in all, the mechanism of the cracks were fatigue cracks, which were mainly induced by the decrease of canopy tensile strength.