This study was conducted to obtain the basic information on salinity tolerance in Italian Ryegrass. Seeds of 20 cultivars that contained diploid(9 cultivars) and tetraploid(l1 cultivars) types were exposed to eight levels of NaCl concentration ranging from 0 to 350 mM under three levels (15$^{circ}C$, 2$0^{circ}C$ and $25^{circ}C$) of temperature. There were highly significant differences in germination percentage among the levels of NaCl concentration, levels of temperature and cultivars, respectively. Average germination percentage of cultivars in control(no NaCl was higher at 2$0^{circ}C$(90.1%) than that of $25^{circ}C$(87.8%) or 15$^{circ}C$(87.5%). Average germination percentage of cultivars began to decrease over 200mM of NaCl concentration. The degree of decrease in germination was higher at $25^{circ}C$ than that of 15$^{circ}C$ or 2$0^{circ}C$. At 2$0^{circ}C$, the germination percentage and gemination speed were gradually decreased as NaCl concentration increased. The average germination day was lengthened by the increase of NaCl concentration and temperature. The germination percentage in diploid types were higher than that of tetraploid types but the average germination day in diploid types was shortened more than that of tetraploid types, regardless of temperature and NaCl concentration.