Abstract: The grain growth behavior of austenite and the solid solution regularity of second phase particles for X80 pipeline steel at different heating temperature were investigated by means of metallographic observation and extraction replicas. The results show that the grain size of austenite increased with the increasing of temperature, and the grain size increases rapidly at 1150 ℃. The niobium carbonitride almost dissolved in the matrix at the heating temperature of 1 200 ℃.