Abstract: Experimental matcrial used was jackfruit (Artocarpus heterophgllus Lam.) seed collected in Xinyi County in Guangdong. The moisture content of newly harvested jackfruit seed was around 58.6%. As water content of seeds declined, germination percentage and germination index decreased. Jackfruit seed is very sensitive to desiccation and is defined as a typical recalcitrant seed. When seeds were naturally desiccated, the activity of superoxide dismutase (SOD) in embryonic axes and cotyledons first incresed, and then rapidly decreased. The contents of malonaldehyde (MDA) and lipid hydroperoxide rose dramatically. The reason why jackfruit Seeds were sensitive to desiccation could be that activity of SOD which is a protective enzyme in plant dropped, and that the peroxidation of membrane-lipid was accelerated. Therefore, the structure and function of membrane were damaged, and then seed viability lost.