Abstract: The microstructure, dislocation and precipitation phases of X80 pipeline steel produced with different processes were analyzed by optical microscope and transmission electron microscope contrastively, and the influence of structure pattern on the performance of X80 pipeline steel was studied combining with tests of mechanic properties. The result shows that the effects of acicular ferrite grain size, precipitate phrase distribution, dislocation density and form on the material strength, toughness and brittle transmission temperatures were distinct, and solid solution strengthening, fine crystal strengthening, dislocation strengthening and precipitation strengthening were the strengthening ways of X80 pipeline steel.