This study investigates the effect of copper on the germination and growth of watermelon plants. It was found that copper only inhibited the germination and growth of watermelon plants when its concentrations were high. Copper concentrations of either 50 or 100μM increased chlorophyll content in the plants slightly while copper concentrations over 100μM led to an obvious decrease in chlorophyll contents. It is concluded that excess copper significantly affects the germination and growth of watermelon.