Manhom (Dioscorea alataL.) was native yam of Thailand. It was edible plant. The objectives of this research were 1) to study morphology, 2) to observe phenological cycle and 3) to determine nutritional value of manhom in Suratthani province. These research was devided in to 2 experiments. The first experiment was to study morphology of manhom from 11 districts and to study the phenological cycle of manhom at Ban-nasan district, Suratthani province. Ten plants were selected to collect data every 15 day. The second experiment was to determine the amount of nutrition in tuberous root of manhom in 2 stages, mature leaves and dormancy leaves, The nutritional value were compared by t-test. Over a period of one year of studying manhom, findings showed that manhoms were found in 11 districts of Suratthani province. Leaf shapes were cordate, young stem and young leaves were violet as well as the young stems were violet with archeh and wings. Manhom tuberous roots were 3 types 1) round – big with jagged edge 2) long – flat with jagged edge and 3) round-long. The fresh tuberous root of manhom were violet, violet with yellow and violet with blue. The tuberous root weight were between 0.5 – 2.7 kilograms. The bulblets grew up along the green 2 mature aerial stem of manhom. Inflorescences of manhoms consisted of many yellow floret. Fruits were three locules. The vegetative phases of manhom in Amphur Ban- nasan, Suratthani province were devided in to 3 stages. 1) Leaf bud formation and expansion. 2) Bulblet setting. and 3) Leaf dry and falling. All plants exhibited peak bud formation between mid March and early April and bud break in mid April. Leaf expansion continued up to early October. Bulblets occurred in early October and grew up until dry leaves, mid December. Leaves senescence and dry in mid October and reached 100 percentage in mid December. The low temperature were effected to young stem and young leaves. Manhoms in 11 districts of Suratthani province contained not only carbohydrate, protein, but also fat, potassium,calcium, magnesium, sodium, vitamin B2. vitamin C, vitamin E, folate and niacin. The moisture, fat, phosphorus,calcium, magnesium and vitamin C of manhom in 2 stages were highly significant.