Abstract: To solve the problem of water plugging of 101.6 mm cased hole, water plugging string with release based on Y341-80 packer is developed. The string consists of release, Y341-80 packer, and ball seat. After setting hydraulically, upper setting and lower production could be fulfilled. The middle layer could be blocked and the upper and lower layers could be produced. is designed, and the release could be continually, so the operation procedures are simplified. The newly developed water plugging string has been applied to 16 wells and it can be used to solve the problem of water plugging of 101.6 mm casing.