A method for preparing a soy leghemoglobin includes: constructing a first plasmid containing genes for heme biosynthesis pathway enzymes; constructing a second plasmid containing gene for Glycine max leghemoglobin LGB2; constructing a first Escherichia coli production host containing the first plasmid and the second plasmid; and producing the soy leghemoglobin by culturing the first Escherichia coli production host. A composition useful as a meat flavor and/or an iron supplement includes the soy leghemoglobin prepared in accordance with the method.