Abstract: The nominal yield ratio, true yield ratio and static toughness of five normal steels were calculated and the engineering stress, true stress and true strain curves were tested to analyze the effects of yield ratio rising on the use security of pipeline steels. The results show that the nominal yield ratio increased gradually and the plasticity index decreased with the increase of the strength level. Comparing with the nominal yield ratio, it was more objective to use the true yield ratio to characterize plastic deformation, and the nominal yield ratio magnified the potential safety hazard caused by raising yield ratio. The yield ratio of X80 pipeline steel was high, but its capability of resisting deformation did not decrease. It would cause unnecessary waste to require fairly low yield ratio for high strength pipeline steels.