Abstract: Vicia sativa L. is an important leguminous green manure plant. The results of the experiments indicated that lateral roots near the soil surface developed abundant nodules housing Rhizobium bacteria that fixed atmospheric nitrogen. The average fresh weight of nodules per plant was 22.3 grams. The nitrogen fixing activity reached a maximum in the branching stage and declined during the first flowering stage. The nitrogenase activity was particularly affected by high temperature. The results of the experiments showed that the activity varied little in the range of 0-25℃.The maximum activity was at 20℃.The activity was markedly reduced at 30℃ or -5℃. Approximately 47-124 kg of nitorgen per mu was fixed by nodulated Vicia sativa. L. during the growth period under the experimental condiditions.