Abstract: Aided by multiple analytical detection techniques, the microstructure and tensile properties at room temperature of low-alloy high-strength light weight steel were investigated. The results show that after TRIP treatment at 780 ℃/200 s+420 ℃/300 s, the 0.18C-2.1Mn-0.45Si-3Al cold-rolled steel exhibits the tensile strength above 1100 MPa and the product of strength and elongation over 26000 MPa·%, resulting from the transformation induced plasticity effect of retained austenite in the microstructure. The contribution of various strengthening mechanisms to the yield strength of experimental steels can be evaluated by an empirical model, which shows that the solid solution strengthening is the main strengthening mechanism. The contribution of dislocation strengthening and grain boundary strengthening makes the strength of cold-rolled steels significantly higher than that of hot-rolled steels. The more ferrite content and a higher proportion of high angle grain boundaries make hot-rolled steels exhibit more ideal plasticity.