Abstract: Ø177.8 mm tie back double-stage cementing technology is adopted in the design of Well Shunnan 5-1 in Tahe Oilfield. Second-stage circulation passage isn formed after first-stage cementing, so second-stage cementing cannot be carried out. Based on the structure and working principle of double-stage mechanical collar, two trips were conducted for downward tapping and downward closing respectively so as to guarantee its well integrity. Based on analysis, it is eliminated that ground equipment and double-stage collar are the reasons for the failed formation of circulation passage of two-stage cementing, and it is determined that the reason for this complex situation is that the lead slurry of first-stage cementing slurry cannot flow after it is thickened due to long-time stillness. According to the analysis results, the tie back double-stage cementing technology is improved and the setting of the casing centralizer optimized. It is recommended to carry out tie-back insertion for the tapping of stage collar after cementing completion, and then set the mandrel hanger. And the properties of slurry shall be tested before the cementing, so that the similar complex situations can be avoided effectively. Theresearch results provide the valuable reference for the solution of similar well integrity.