In this study, four genotypes (Tunceli, Amasya, Malatya and Urfa), one standard type (Galactica) and one F1 hybrid varieties (Golden Crown) watermelon were used. Watermelon seedlings were grown in water culture using Hoagland nutrient solution in atmosphere-controlled climate chamber. When the plants had developed four to five true leaves, salt treatment was began, and 100 mM NaCl was gradually applied to medium. The purpose of this study was to investigate whether seed size and cotyledon weight may be used as a marker for salt-tolerant. As a result, genotypes with large seeds and cotyledons had higher enzyme activities than ones with smaller seed and cotyledon. Malatya ve Urfa with larger seed and codyledon leaf were less affected by salt damage, probably because they run better antioxidant enzymes. Galactica and Golden Crown F1 with smaller seed and cotyledon were more affected from slat damage, employing at a lower level of enzyme activities.