Abstract: With the development of oil fields, the downhole casing status of the oil and water well are getting bad and bad. The problem well of Wenliu Oilfield now has been become 41.9 percent in the whole well number, which control 1058×104t oil reserve. Arm at this problem, the eight arms magnetism combination logging technology has been introduced. The technology include better performance, more parameter, selected combination and advance magnetism logging, which can monitor the oil casing. With 42 wells being logged,28 wells’ casing are reconditioned, which recovered control reserve 120.7×104t and successful rate is 92.9%. The application of this technology not only provide guarantee to the project accuracy and the measure effective, but also provide foundation to the cognition of the reason in downhole casing.