Abstract: To enhance the efficiency of pipeline transmission, a 0.8 design factor has been, for the first time in China, adopted on natural gas pipelines in Class Ⅰ areas in western section of the 3rd West-to-East Gas Pipeline. According to the design requirements, circumferential stresses generated during pressure tests at relatively high design factor shall be no less than 100% SMYS. There is no domestic experience for pressure tests with such high intensities. To ensure proper implementation of heavy-duty hydraulic tests and with consideration to available codes and features of the 0.8 design factor, program for heavy-duty hydraulic tests and process flow for pressure tests have been prepared. p-V curves, stress-strain monitoring, intelligent deformation detection and other techniques have been deployed for the first time to monitor expansion and deformation of pipelines during pressure tests. Test results show first heavy-duty hydraulic tests for natural gas pipelines with the 0.8 design factor in Class Ⅰ areas of China are successful with pressure test program proved to be scientific and rational. Successful execution of these heavy-duty hydraulic tests may provide future heavy-duty hydraulic tests of natural gas pipelines with high design factor with valuable experiences. In addition, they may establish solid foundation for promotion of the 0.8 design factor in Class Ⅰ areas in China.