The influence of tempering temperature on microstructures and mechanical properties of X120 pipeline steels with two different quenching processes, which can be classified as direct quenching process (DQP) and indirect quenching process (IDQP), was studied. The results showed that, the microstructures of two different quenching processes were BF and M and GB, BF and M, respectively. With tempering temperature increasing, the strength of the steels fluctuated, the impact toughness and elongation improved remarkably in tempering temperature range from 400 to 500 ℃. In DQP, the mechanical properties were fluctuating because it led to fracture separation when tempered at 350 ℃ and 600 ℃. However, for IDQP, the stability of mechanical properties was comparatively high during tempering process. Therefore, it is suggested that the process tempering at 450～500 ℃ in IDQP could help obtain a pipeline steel with an excellent mechanical properties, which met the demand of X120 pipeline steel.