Abstract: The microstructure of X120 ultra-high strength pipeline steel and precipitates during its hot deformation were characterized by optical microscope and electronic microscope. The results showed that the Nb-Ti diphase precipitate forms at 1020°C in the austenite recrystallization region when the steel is rolled, thus affecting the grain refinement somewhat. With the accumulated reduction kept unchanged, the effects of heavy reduction and a few number of passes on hot-deformed austenite size are small, while the effects on the deformation bands, substructure, final structure morphology and grain size are comparatively greater to a certain extent. Moreover, the effects of rolling temperature in recrystallization region and rolling schedule for non-recrystallized region on deformation resistance were analyzed.