The non-degradability which earlier had been thought to be a good advantage of using plastic now has been reconsidered the main source of environmental issues, especially the heaps of solid plastics in the ocean. The degradation of plastic can be done using chemical process or by using biodegradation which is safer. Recently, a new bacterial species, Ideonella sakaiensis, was found and isolated that was exposed to use PET(Poly Ethylene Terephthalate) as a carbon source[1-4] and it can degrade PET polymer into monomers of monohydroxyethyl tereph-thalate (MHET), by means of two enzymes PETase and MHETase respectively. The catalytic site is consisting of three amino acids (S131, H208, D177) which form the catalytic triad. the catalytic triad has studied in detail during the simulation of 150 ns and found that these amino acids were quite stable even in the presence of PET. Here we attempt to understand the effect of aqueous ionic liquid on the stability and catalytic activity of PETase since ionic liquids are environment friendly, enhance the stability and catalytic activity of certain enzymes[5-6]. The ligand present is having 2 terephthalate units connected with one ester bond. Three different ionic liquids are [C2mim] [CH3COO], [C4mm] [CH3COO], and [Ch]₃[PO₄] simulated at three different concentration of 40 %, 30%, and 20% in the presence of enzyme PETase docked with the ligand. The structure seems to be quite stable after 150ns simulation in the presence of ionic liquids. The stability of the enzyme is relatively high in cholonium phosphate ionic liquid.