Abstract: This study has investigated the microstructure and properties of Fe-rich multi-principal-element alloys（high entropy steels）. It was found that excellent tensile properties can be obtained at room temperature through cold rolling and aging heat treatment in Fe40Ni30Co10Cr8Al5Ti7, with a yield strength of 1750MPa and a uniform tensile elongation of 11%. The microstructure of the alloy after cold rolling and aging heat treatment was observed to be composed of a heterogeneous structure of a face centered cubic（FCC） matrix and a precipitated L12-structure strengthening phase. The ultrahigh yield strength is the result of the combination of refined-grain strengthening,dislocations strengthening and precipitation-hardening. The high-density stacking faults generated during deformation resulted in excellent tensile ductility of the alloy. This study shows the importance of L12-type ordered precipitates on the improvement of strength and plasticity on the Fe-rich multi-principal-element alloys（high entropy steels）.