Meat color depends on the amount and the state of myoglobin(Mb) in meat,containing 3 types.The red is MbFe2+,the bright red is oxymyoglobin(MbFe2+O2),while the brown is metmyoglobin (MetMb Fe3+) for meat color (Dean and Ball,1960; Ledward,1992).The major factor leading to meat discoloration is iron autoxidation from Fe2+ to Fe3+ form.Since 1990s,it has been found that there is a system of the MetMb enzymatic reduction with the color stability in meat (Echevarne,Renerre & Labas,1990; Lanari & Cassens,1991; Reddy & Carpenter,1991).Some research suggested the activity of MetMb reductase was a controlling factor.It might retard discoloration and regulate the color stability of meat (Cheah & Ledward,1997; Zhu & Brewer,1998).In this research,the objective was firstly to study identification and purification of MetMb reductase from porcine cardiac muscle.