Pea seedlings (Pisum sativum L.) were used as materials to test the timings and compartments of hydrogen peroxide (H2O2) triggered by wounding and exogenous jasmonic acid (JA). The results showed that H2O2 could be systemically induced by wounding and exogenous JA. H2O2 increased within 1 h and reached the peak 3-5 h after wounding in either the wounded leaves or the unwounded leaves adjacent to the wounded ones and the inferior leaves far from the wounded ones. After this, H2O2 decreased and recovered to the control level 12 h after wounding. The activities of antioxidant enzymes, however, were rapidly increased by wounding. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, could significantly inhibit H2O2 burst that was mediated by wounding and exogenous JA. Assay of H2O2 subcellular location showed that H2O2 in response to wounding and exogenous JA was predominantly accumulated in plasma membrane, cell wall and apoplasmic space. Numerous JA (gold particles) was found via immunogold electron microscopy to be located in cell wall and phloem zones of mesophyll cell after wounding.