The spread of SARS CoV 2 across the globe rushed the scientific community to find out the potential inhibitor for controlling the viral disease. The main protease (Mpro) or Chymotrypsin protease (3CLpro) is involved in the cleavage of polyproteins, duplication of intracellular materials and release of nonstructural proteins. Cys-His catalytic dyad is located in the SARS-CoV Mpro which is the substrate-binding site located in domains I and II. There are many approved drugs that have their active protease inhibition capability. The targeting of the active site of the main protease is the better option to fight against the viral population. Lopinavir, ritonavir, Remdesivir and Chloroquine are some of the drug candidates considered to be involved in the treatment of SARS CoV 2 under emergency situation as a trial basis. In the present investigation we used lopinavir as a drug to bind the catalytic dyad His41, Cys145 of main protease. The minimum binding of energy of -11.45 kcal/mol observed with the binding of Cys145 and -10.93 kcal/mol was noted with the residue His41. The inhibition constant was also found to be relevant to the binding efficiency of the drug. This is considered to be a model drug target which is initiating the finding of many new drugs to target the current outbreak created by the virus SARS.CoV - 2.