Continues cooling phase transformation behavior and strengthening mechanisms of the Ti-containing steel were systematically studied by thermal simulation testing machine, high-resolution transmission electron microscope and metallographic microscope. The result showed that the microstructure was mainly composed of ferrite and pearlite at the low cooling rate (0.5-1 ℃/s). When the cooling rate was gradually increased (1-5 ℃/s), the bainite structure appeared and the ratio of bainite increased. And the microstructure mainly consisted of bainite at the high cooling rate (5-10 ℃/s). The strengthening mechanisms of the Ti-containing steel were precipitation strengthening and fine-grain strengthening. TiN mainly precipitated as fine particles dispersing and its size was 10-20 nm. The optimized cooling rate was (1.5±0.5) ℃/s for the 20 mm HRB400E steel industry trial production, the yield strength was above 430 MPa, the elongation after fracture was above 20%, the maximum gross elongation was above 15%, and the ratio of tensile strength and yield strength was above 1.4.