Abstract: Seeds of different ploidy watermelon were evaluated for germination under 0,30,60,90,120,150,180,210 mmol/L NaCl stress. The results showed that relative germination percentage of different ploidy watermelon seed have no significant difference under low NaCl concentrate, however there was significant decreased over 120 mmol/L NaCl concentrate . At 150 mmol/L, relative germination percentage among M4x、M3x、M2x was 77.8%、63.4%、30.6%, respectively. their relative germination percentage was 37.8%、31.7%、0 at 180 mmol/L, respectively. At 210 mmol/L , several seeds of M4x was germinated. The seeds salt-resistance qualities of different ploidy watermelon were: M4x＞M3x＞M2x.