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Background: The severe acute respiratory syndrome (SARS) is a life threatening viral infection caused by a positive, single stranded RNA virus from the enveloped coronaviruse family. Associated with fever, cough, and respiratory complications, the illness causes more than 15% mortality worldwide. So far, there is no remedy for the illness except supportive treatments. However, the main viral proteinase has recently been regarded as a suitable target for drug design against SARS infection due to its vital role in polyproteins processing necessary for coronavirus reproduction. Objectives: The present in silico study was designed to evaluate the effects of anti HIV-1 proteases inhibitors, approved for clinical applications by US FDA, on SARS proteinase inhibition. Methods: In the present study, docking and molecular dynamic experiments were applied to examine the effect of inhibitors on coronavirus proteinase under physiological conditions of similar pH, temperature, and pressure in aqueous solution. Hex software version 5.1 and GROMACS 4.5.5 were used for docking analysis throughout this work. Results: The calculated parameters such as RMSD, RMSF, MSD, dipole moment, diffusion coefficient, binding energy, and binding site similarity indicated effective binding of inhibitors to SARS proteinase resulting in their structural changes, which coincide with proteinase inhibition. Conclusions: The inhibitory potency of HIV 1 protease inhibitors to cronovirus proteinase was as follows: LPV > RTV > APV > TPV > SQV. Lopinavir and Saquinavir were the most and the least powerful inhibitors of cronovirus proteinase, respectively.