Abstract: The end quenching test is a test method to determine the hardenability of steel, and the hardenability directly affects the service performance of steel products. A company has developed a kind of automatic end quenching test device for detection hardenability of steel parts, and the hardenability of 45 steel, 34CrMo4 alloy steel, 40NCD7-03 steel and a major engineering steel were tested by this device. The results show that the automatic end quenching test device meets the requirements of GB/T 225-2006 and other test methods. The quenching depth of 45 steel was about 5 mm, that of 34CrMo4 alloy steel was 7-10 mm, and that of 40NCD7-03 steel was more than 50 mm. The hardenability of a major engineering steel was the best when the quenching temperature was 1 050 ℃.