Peroxynitrite　is　a　highly　reactive　oxidant　that　has　been　implicated　in　a　number　of　serious　human　diseases　including　cardiopathy,　acute　inflammation　and　cancer.　The　decomposition　of　peroxynitrite　can　be　promoted　efficiently　by　metalloporphyrins　and　are　therefore　important　to　detoxify　the　cytotoxic　oxidant　as　therapeutic　agents.　A　novel　cobalt　porphyrin　was　synthesized　to　investigate　the　scavenging　effect　on　peroxynitrite　decomposition.　Kinetics　of　peroxynitrite　decomposition　in　the　presence　of　cobalt　porphyrin　was　investigated　by　UV-Vis　spectrophotometer　and　stopped　flow　instrument.　The　kinetic　experiments　reveal　that　cobalt　porphyrin　could　accelerate　the　decomposition　of　peroxynitrite　and　the　catalytic　ability　is　improved　with　the　increasing　concentration　of　cobalt　porphyrin.　The　study　is　helpful　to　develop　more　effective　scavengers　of　peroxynitrite　in　order　to　treat　related　diseases