The wear of casing threaded joints is one of the important reasons affecting the sealing and structural integrity of casing strings.Due to the complex structure of casing threaded joints,there are few studies on the mechanical properties of casing threaded joints under wear conditions.The finite element model of the special thread of TPCQ was established,and the stress distribution and sealing performance of the worn casing threaded joint under the action of internal pressure and external pressure were analyzed.The results show that the residual strength of the thread decreases with the increase of the wear depth.When the wear depth reaches 4 mm,the burst strength,collapse strength and tensile strength decrease by 22.9%,26.1% and 18.2%,respectively,and the sealing performance parameter is less than the critical sealing index,so there is a risk of leakage in the threaded seal.The proposed method can quantitatively evaluate the residual strength and sealing performance of casing threaded joints,which provides a theoretical basis and technical basis for the evaluation and verification of casing residual strength.