The main aim of this research is to provide literature of the Ocimum plant, to know the significance of the Ocimum species carried out by pharmacognostical study and experimental design for GC-MS.Ocimum genus is very important for its therapeutic potential. among the most important aromatic herbs for their enormous medicinal properties. Extreme Attention has been put on those literature reports wherein the utilization of Tulsi and their pharmacognostical study has been done by performing morphological and microscopic leaf and experimental design by using essential oil by GC-MS instrumentation method. The utilization of these characteristics would be important for the drug discovery scientist to develop a specific formulation of the crude drug, which will be a magical therapeutic agent in the future, with the many advantageous. GC-MS chromatogram of the Ocimum sanctum, Ocimum canum and Ocimum gratissimum oil showed major peaks and has been identified after comparison of the mass spectra with NIST library, indicating the presence of three photo components. From the results, GC-MS study suggested that anethole which is well reported antimicrobial compound is more in O. canum (2.66%) in comparison to O. sanctum (1,28%) but absent in O. gratissimum. The results indicated that the antimicrobial activity is more in O. canum due to the present high amount of anethole in comparison to O.Gratissimum, and O. Sanctum. The GC-MS study suggested that anethole which is well reported antimicrobial compound is more in O. canum (2.66%) in comparison to O. sanctum (1,28%) but absent in O. gratissimum. The result revealed that O. canum has a microscopic character, that can be identified by the characteristic GC MS analysis of extracts, to distinguish between different species of the ocimum plant.