Experiments were conducted to study the stability performance over two environments for seed yield in mung bean lines in organic system during the rainy and dry seasons of 2018 at Maejo University and Maerim district, Chiang Mai. Six potential mung bean lines were evaluated with 2 standard varieties by using randomized complete block design with 3 replications. The analysis of variance at individual location showed mung bean line 15 and KPS2 gave the highest yielding ability and showed yielding stability for widely adaption in all seasons and all locations. Wide adaptability in all seasons and high yield potential were 183.18 and 179.62 Kg./rai respectively