Plant peroxidase (EC: 1.11.1.7) a heme-containing protein which is widely used in plants, microorganisms and animals. This two - substrate enzyme, catalyze the hydrogen peroxide into water with   oxidation of many organic and inorganic substrates that all of them can be used to measure enzyme activity. Although it’s specific substrate is hydrogen peroxide. Calcium and at least four disulfide bonds in the protein structure lead the formation and strength of three-dimensional structure of the molecule. Plant peroxidase has several roles including, involvement in lignin biosynthesis, auxin metabolism, cell growth, cell wall cross linking and respond to environmental stress. So peroxidase, considered as a good point to pursue the cell deal with stress factors such as oxidative stress. These days according to produce the pure samples of this molecule, peroxidase also used in ligand-protein studies in pharmaceutical research. So in this brief overview, in addition to introducing plant peroxidase we have had a brief look to measure the enzyme activity, the number of isoenzymes in a cell and the ensuing conformational changes of peroxidase.