In semi arid zone of southern Tamilnadu, India farmers are recognized that planting with multipurpose nitrogen fixing trees including medicinal plants in an agroforestry system for sustainable income generation.To identify the existing agroforestry system. A systematic survey was carried out to find out the nitrogen fixing trees planted in the agroforestry system revealed that a total of economically important 9 tree species belonging to 8 genus of 3 families were commonly cultivated without specific model. These multipurpose usable trees improve soil physical properties, maintain soil organic matter, fix the atmospheric nitrogen and promote nutrient cycling through high amount of litter production, which increase the main crop yield.