Abstract: The Chaheji-Renqiu Oil Pipeline, with the capacity of 3600 t/d and 36 km (ϕ219×7 mm) in total length, constructed and put into operation in 1993. There was something wrong with the cathodic protection found in a 18-km-pipe-section of the pipeline in 1995. On the basis of results of site investigation, the opposite potential protection method was determined to use to improve the cathodic protection. The applied results indicated that this method, compared with the establ ishment of cathodic protection station and sacrificial anode method, was cost-effective. This pipeline has been well protected with this method since 1998.