Abstract: Because of overtime of service, corrosivity of media and erosion, internal corrosion of oil and gas pipelines has been more and more serious. However, the main way to detect internal corrosion is of single point ultrasonic testing, which cannot cover the whole corrosion region on the pipeline, and we may therefore fail to discover the faults and to learn the status of corrosion of pipelines accurately. According to this, in this paper we have studied the technology of ultrasonic C-Scan by investigating well-known checkout equipments at home and abroad and comparing the results of laboratory experiments with field tests. Finally, we come to a conclusion that the technique of ultrasonic C-Scan has many advantages such as higher detection efficiency, higher detection rate, higher accuracy and higher image resolution. This paper has put forward a new nondestructive testing technology for pitting detection, whose result will provide powerful technological support for corrosion monitoring, residual intensity evaluation and residual life prediction of pipelines.