Abstract: The microstructure and mechanical properties of a new type of hot-rolled Fe-0.4C-10Mn-1.8Al-0.6V(medium manganese)steel were studied.The results show that with the increase of annealing time from 30 min to 60 min, the volume fraction of retained austenite decreases, the stability improves, and lath martensite gradually transforms into acicular martensite. Due to the discontinuous TRIP effect, the serrated fluctuation is observed in the tensile curve, and the yield strength, tensile strength and total elongation decrease with the extension of annealing time. The experimental steel has good mechanical properties after 30 min annealing at 800 ℃, the yield strength is 670 MPa, the tensile strength is 1230 MPa and the total elongation is 18.3%.