The microsturcture characteristics of 42CrMo steel in asrolled and thermomechanical treated conditions were researched. The results of thermomechanical deformation experiment showed that when the specimens were held at 650-750 ℃ for 300 s after deformation at strain 12 and then were annealed at 700 ℃ for 2 h, the achieved microstructures were similar to those in asrolled condition and soaking for long time (≥16 h ). Therefore, the time of traditional annealing process can be significantly shortened.