The peroxidase (POD) isozymes in 4 watermelon hybrids and their parents were analysed by using polyacrylamide gel disc electrophoresis. The variation of POD isozymes in the proseeding of seed germination and growth and the distribution of the isozymes in different organs at cotyledon stage were disccused. No certain relationship between the advantages of watermelon hybrids and their zymogram types of POD isozymes was found. The zymogram of POD isozymes in dry seed at storage stage cannot be used for identifying watermelon hybrid, and the zymogram in plantlet at germination stage only can be used to identify a part of watermelon hybrids.