Abstract: In this paper, a blowout preventer shell with crack was tested when it was pressurized by using acoustic emission(AE) technique. A notch of 100 mm long and 5 mm wide was cut in a scraped bop shell, and then it was welded and pressurized with pneumatic pumps. We tested the bop shell during pressurizing, the result showed that the AE technique could reflect the activities of the defects timely and effectively, and the damage situation of the blowout preventer shell in the pressured process and the location was accurate.