Microstructure and mechanical properties of warm rolled 7Mn steel undertaken different intercritical annealing (IA) were studied in this work. It is found that the deep-cryogenic treatment (pre-DCT) process change the composition and grain size of austenite of the steel after IA. With IA temperature decreasing, the enhancement effect of the pre-DCT on mechanical properties is remarkable. UTS×TE of the pre-DCT specimen IA at 600℃ is almost doubled. Austenite and ferrite grains exhibit different morphologies, both equiaxed and lamellar. Moreover, the serration behavior on engineering stress-strain curves is postponed, work hardening (WH) rate decreases, both of which are mainly caused by the increasing stability of austenite. The volume fraction, morphology and composition of austenite and the stability of RA could be tailored by modifying processes. The pre-DCT + IA at 645℃ for 4h specimen exhibits the best UTS×TE, 41 GPa·%.