The objective of this study was to find out the effects of salinityand light to the seed germination of mung bean (Vigna radiataL.) which had been conditioned for three treatments, namely the first sample of mung bean was placed on the medium with any direct sunlight, the second one was placed on the medium without any sunlight (in the dark) and the third one was placed on the medium with less sunlight. This study was conducted in the Experimental Greenhouse ofFaculty of Mathematics and Natural Sciences, The State University ofMedanon October 2015 for five days (approximately 120 hours). The researcher selected the mung beanfor this study due to its short life cycle so thatit was more easily to be observed and experimented as well. The method of data collectionused the documentation and measurement, and also the description and quantitative technique was applied in this experiment. The results showed that salinity and light significantlyinfluenced the seed germination of mung bean. The seeds of mung beanwhich were treated to 0% of salt on themedium with any source of sunlight had a better growth of germination rather than those seeds with 0% of salt on the medium without any sunlight as well as less sunlight. The seeds of mung beanwith 2.5% of salt in the dark and light condition still had a low germination,meanwhile those seeds were placed on the medium with less light had no germination occurred. The seeds of mung bean with the concentration of 5%, 7.5%, and 10% consecutively upon three treatments showed no germination processes until the end of the observation. This has been shown that salinity and light had the very significant effects to the germination process of mung bean.