Abstract: To meet the need by operation of drilling slim hole, shallow well for which the airtight conditions are not so strict, a HG-FJ economical extreme-line casing is designed and developed.Detailed here in the paper are the development activities and application of this casing.Based on relevant analysis it is regarded that the HG-FJ casing has met the requirements for sealing and strength of the thread connection via the interference-fit of the thread connection and the design of hook type thread structure;and that the thread connection exhibits good gallingresistance after its surface is shot-blasted.The casing product has been proved to be satisfactory to the requirements for the actual oil field operation conditions.