Abstract: Safety and integrity inspections of river-crossing segments in long-distance oil and gas pipelines are essential, yet traditional methods often face challenges such as low efficiency, high risks, and insufficient accuracy. This study discusses the principles and methods of using Remotely Operated Vehicle (ROV) technology for intelligent inspection of pipeline river-crossing segments. It introduces the River-Remotely Operated Vehicle (River-ROV) external corrosion detection system, which integrates pipeline positioning, burial depth measurement, Two-Dimension (2D) imaging sonar, cathodic protection potential measurement, and potential gradient detection. Using the segment where the Sichuan-to-East Gas Transmission Pipeline crosses the Qingyi River by open-cut excavation as a case study, the advantages of ROV technology for integrity inspections of river-crossing pipeline segments are further demonstrated. ROV technology can effectively detect the cathodic protection and external anti-corrosion coatings of pipelines in river-crossing segments, provide data support for gas pipeline integrity assessment, and make important contributions to the development and application of underwater intelligent inspection technologies.