Abstract: The corrosion inspection of steam generator tubes is an important problem which ensures the security of the nuclear plants. The most conventional corrosion of the tubes are corrosion dots. Based on the principle of acoustic emission technique, acoustic emission signals about tubes of steam generator gathered by instrument were analyzed, and the corrosion dots in the tubes were located accurately. The results show that corrosion dots of heat transfer tube are through three phases: Development period, stable period and rapid development period. Acoustic emission technique can be found earlier corrosion damage than any other non-destructive testing methods. The real-time inspection on the work of steam generator was achieved, according to which the corrosion dots can be judged timely.