In the current investigation 3 medicinal plants i.e. Datura metel, Achyranthus aspera and Euphorbia hirta were selected and used for screening of major bioactive constituents of medicinally importance plants. For this study methanolic extracts of leaves and stems of these plants were prepared and used for the qualitative and quantitative screening. These plants were found to contain carbohydrates, phenols, tannins, saponines, glycosides, proteins and alkaloids. Alkaloids, carbohydrates and flavanoids were present in methanolic extracts of leaves and stems of all three plants. Maximum numbers of phytoconstituents were found in A.aspera then followed by E.Hirta and lowest was in D.metel. Quantative analysis showed the total phenolic content were 8.3, 9.1 and 7.7 mg/g in leaves and 5.9, 6.5 and 4.8 mg/g in stem of D.metel, A.aspera and E. hirta respectively. Estimation of total flavanoids contents were 16.4, 19.3 and 13.5 mg/g in leaves and 9.6, 12.3 and 7.9 mg/g in stem of D.metel, A.aspera and E. hirta respectively. Due to rich source of phytochemicals this plant is may be used for herbal medicine