A kind of C- Si- Mn series (0.14C-1.4Si-2.72Mn) tested steel was designed,and the CCT curves andphase transformation rules of the steel were measured by using a thermal dilatometer.Then,the microstructure andphase distribution of the tested steel sheet after hot- rolling and annealing were analyzed by means of OM,SEM,TEM and EBSD.Finally,the retained austenite content of the tested steel was measured by means of XRD.Theresults show that (1) the designed 0.14C-1.4Si- 2.72Mn tested steel possesses good hardenability and is of a criti-cal cooling rate of 10.00℃ /s; (2) the microstructure of annealed tested steel sheet is mainly composed of martens-ite,ferrite and a little amount of retained austenite; (3) the martensite is partially tempered,and the retained aus-tenite accounts for 4% ～6% and mainly distributes among martensite laths but partially distributes in the ferrite;(4) after the annealing of the tested steel sheet,the tensile strength and the total elongation reach 1333MPa and13%,respectively,and the tensile strength accords well with the ductility.