Abstract: For the section of the 3rd West-to-East Gas Pipeline with 0.8 design coefficient, high testing pressure is required on site. In this paper, a system analysis is made on the relationship between testing pressure level and residual defects, judging criteria of yield deformation under the testing pressure, calculation of accumulated plastic strain and p-V curve in the pressure-volume control method. The results show that high testing pressure can help to significantly reduce the residual defects; the testing pressure and actual yield strength are the main factors affecting the yield of the pipeline. If the actual yield strength of testing pipeline section is less than 93% SYMS, yield deformation will occur. When the pressure increases to the max. testing pressure, cumulative plastic strain is connected with its actual intensity. The void fraction of pipe filled with water and the low strength steel pipes have great impact on p-V curve.