The focus of the present research work is on evaluation of the antimicrobial finished textile material from the extract of Aerva lanata plant and optimization of process parameters to get the maximum antimicrobial efficiency. The microencapsulated extracts of Aerva lanata plant (leaves and stalk) using citric acid as a cross linking agent were applied on plain-woven cotton fabric by pad-dry-cure method. The Aerva lanata extract treated fabric samples were tested for antibacterial activity against bacterial strains of Staphylococcus aureus and Escherichia coli under Agar diffusion test and AATCC 100-2004. It is observed that the treated cotton fabric shows a clear microbial resistance of about 19-25 mm zone of inhibition in the agar diffusion test against the above-mentioned bacterial strains. The treated samples showed 80 % of reduction against Staphylococcus aureus and 70 % reduction against Escherichia coli as per AATCC (100-2004). Process parameters like concentration of extract, citric acid and curing temperature were optimized using Box-Behnken design for better performance of antimicrobial treated material. The optimum values of 21.14 % extract concentration, 2.39 % cross-linking agent and $101.2^{circ}C$ curing temperature were determined.