Given the significant importance of mechanical gauging and pressure testing for submarine pipelines in offshore pipeline construction， this study focuses on reviewing the requirements for mechanical gauging and system pressure testing as outlined in the ASME， API， and DNV standards. By explaining the principles of submarine pipeline mechanical gauging， the calculation methods for gauge-plate diameters under different standards are analyzed. Based on the principles of pipeline pressure testing， it is clarified that test pressure and holding time are the two critical parameters in pipeline pressure testing. The magnitude of the test pressure depends on the size of the defects that need to be detected during the test. The duration of holding time is influenced by multiple factors， including the size of leaks， pipeline volume， and pipeline diameter. Although ASME， API， and DNV share similar general principles for submarine pipeline pressure testing， differences exist in the selection of test pressure and holding time， which necessitates an analysis of their applicability in engineering practice.