The objective of this research was to determine the chemical composition of aerial parts extract from methanol. The phytochemical compound screened by gas chromatography-mass spectrometry (GCMS) method. Thirty one bioactive phytochemical compounds were identified in the methanolic extract of Ocimum basilicum. The identification of phytochemical compounds is based on the peak area, retention time molecular weight, molecular formula, MS fragmentions and pharmacological actions. GC-MS and Fourier transform infrared (FT-IR) analyses of O. basilicum revealed the existence of Paromomycin, Stevioside, Campesterol and Ascaridole epoxide, aliphatic fluoro compounds, alcohols, ethers, carboxlic acids, esters, nitro compounds, alkanes, H-bonded H-X group, hydrogen bonded alcohols and phenols. Methanolic extract of bioactive compounds of O. basilicum was assayed for in vitro antibacterial activity against Pseudomonas aerogenosa, Proteus mirabilis, Escherichia coli, Staphylococcus aureus and Klebsiella pneumonia by using the diffusion method in agar. The zone of inhibition was compared with different standard antibiotics. The diameters of inhibition zones ranged from 5.70±0.10 to 0.55±0.29 mm for all treatments.