The Wafangdian area of Liaoning Province is famous for the abundant primary diamond of kimberlite type. More than 100 kimberlite bodies have been found, and the proven diamond resources/reserves account for more than half of the country. In particular, the diamond quality of No.50 Kimberley rock tube is the best, with the gem-quality accounting for 70 %, and the quality was the world-class, but it suddenly pinches or disappears down. Predecessors believe that it should belong to the root phase, there is no lower ore body. In recent years, it is believed that the reason for this phenomenon may be the reverse fault dislocation at the bottom of the rock tube, but the direction and displacement of the dislocation are unknown, which brings great difficulties to deep prospecting. On the basis of detailed field geological survey, the thrust nappe structure was first discovered in this area. It is proved that the fault at the lower part of the staggered No. 50 Kimberley rock tube is a secondary reverse fault above the thrust nappe surface, determined movement direction and estimated nappe displacement .Verified by drilling, the nearly 10m Kimberley rock mass was successfully obtained breccia, and a nearly 1 mm pure diamond was accidentally obtained in the thin section identification process, which proved that the rock mass had good ore-bearing property. Based on the theory of thrust nappe structure, underlying ore body of No. 50 kimberlite pipe was successfully found, which pointed out a new direction for deep prospecting in Wafangdian diamond metallogenic belt.