Abstract: Y344-110 inspecting leakage pipe string was designed to resolve the problem of Jiang-453 that packer rubber being damaged easily and flow controller being not seal well. The new development packer Y344-110 and ?100mm flow controller were used in this pipe string. After field testing in 16 wells, the problem that the hole diameter with casing deformation which larger than 110mm has been settled. The packer rubber has not been damaged with many times pipe string setting. Between flow controller core and valve seat, there is soft seal, so sealing property is well and opening pressure is stabilization. The success rate was improved from 30% to 100%.